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I had to quit my job two years before to avoid any issues with the Soviet government. Every programmer I knew had to sign a special form commanding them to keep state secrets. Such a signature could prevent us from getting exit visas. To refresh my skills and to become more marketable, I had to take programming course for six months. In the USSR, they were still a novelty. There were not a lot of practical usage.
Some of the reasons were planed organization of economy, politicized approach to science. Cybernetics was considered "capitalist" discovery and was in exile in s.
In the United States, computers were already widely in use, and even in consumer settings. The other difference is gender of this profession. In the United States, it is more male-dominated. In Russia as I was starting my professional life, it was considered more of a female occupation. Guys would go for something that was considered more masculine. These choices included majors like construction engineering and mechanical engineering. Now, things have changed in Russia.
It, like in the United States, has become a male-dominated field. In conclusion, I have to say I picked the good profession to be in. Although I constantly have to learn new things, I've never had to worry about being employed.
When I did go through a layoff, I was able to find a job very quickly. It is also a good paying job. I was very lucky compared to other immigrants, who had to study programming from scratch.
The last native Multics system was shut down in Along with the simulator an accompanying new release of Multics -- MR And yes, someone has already installed Multics on a Raspberry Pi.
Version 1. Plus there's also useful Wiki documents about how to get started, noting that Multics emulation runs on Linux, macOS, Windows, and Raspian systems. The original submission points out that "This revival of Multics allows hobbyists, researchers and students the chance to experience first hand the system that inspired UNIX. I was a project administrator on Multics for my students at MIT.
It was a little too powerful for students, but I was able to lock it down. But it was still command line based. Considering that processor was likely made with the three micrometer lithographic process, it's quite possible to make the processor in a homemade lab using maskless lithography. Hell, you could even make it NMOS if you wanted.
So yeah, emulation isn't the end, it's just another waypoint in bringing old technology back to life. More importantly: To take some of the things that Multics did better and port them to Unix-like systems. Much of the secure system design, for example, was dumped from early Unix systems and was then later glued back on in pieces.
From here [wikipedia. The design and features of Multics greatly influenced the Unix operating system, which was originally written by two Multics programmers, Ken Thompson and Dennis Ritchie. Superficial influence of Multics on Unix is evident in many areas, including the naming of some commands. But the internal design philosophy was quite different, focusing on keeping the system small and simple, and so correcting some deficiencies of Multics because of its high resource demands on the limited computer hardware of the time.
The name Unix originally Unics is itself a pun on Multics. The U in Unix is rumored to stand for uniplexed as opposed to the multiplexed of Multics, further underscoring the designers' rejections of Multics' complexity in favor of a more straightforward and workable approach for smaller computers. Ken Thompson, in a transcribed interview with Peter Seibel[20] refers to Multics as " It was close to unusable.
They i. None of them were much good at either building or marketing mainframe computers. So yes, Multics was a commercial failure; the number of Multics systems that were sold was small. But in terms of moving the computing and OS state of the art forward, it was a huge success. Security was a major focus in the design of Multics, which led to it being adopted by the military and other security-conscious customers.
It was built at a time when the language was considerably more stable and well defined than it had been when the first compilers were built [1,2]. It has benefited from the experience of the first compilers and avoids some of the difficulties which they encountered. At the time this paper was written most language features were implemented by the compiler but the run time library did not include support for input and output, as well as several lesser features. Inter-process communication Multics tasking may be performed through calls to operating system facilities.
The compiler and its object programs operate within the Multics operating system. Each segment is a linear address space whose addresses range from 0 to 64K.
The entire virtual store is supported by a paging mechanism, which is invisible to the program. Each program operating in this environment consists of two segments: a text segment containing a pure re-entrant procedure, and a linkage segment containing out-references links , definitions entry names , and static storage local to the program. The text segment of each program is sharable by all other users on the system. Linking to a called program is normally done dynamically during program execution.
The EPL compiler was built by a team headed by M. McIlroy and R. Morris of Bell Telephone Laboratories. The extremely short development time of 18 months was made possible by these powerful tools. The same design programmed in a macro-assembly language using card input and batched runs would have required twice as much time, and the result would have been extremely unmanageable.
The project's design decisions and choice of techniques were influenced by the following objectives:. The compiler's size and speed were considered less important than the above mentioned objectives. Each phase of the original compiler occupies approximately 32K, but after the compiler bas compiled itself that figure will be about 24K.
The original compiler was about twice as slow as the Multics Fortran compiler. It is not an interactive compiler nor does it perform partial compilations. A phase is a set of procedures which performs a major logical function of compilation, such as syntactic analysis. A phase is not necessarily a memory load or a pass over some data base although it may, in some cases, be either or both of these things. The dynamic linking and paging facilities of the Multics environment have the effect of making available in virtual storage only those specific pages of those particular procedures which are referenced during an execution of the compiler.
The internal representation of the program being compiled serves as the interface between phases of the compiler. The internal representation is organized into a modified tree structure the program tree consisting of nodes which represent the component parts of the program, such as blocks, groups, statements, operators, operands, and declarations.
Each node may be logically connected to any number of other nodes by the use of pointers. Each source program block is represented in the program tree by a block node which has two lists connected to it: a statement list and a declaration list.
The elements of the declaration list are symbol table nodes representing declarations of identifiers within that block. The elements of the statement list are nodes representing the source statements of that block. Each statement node contains the root of a computation tree which represents the operations to be performed by that statement.
This computation tree consists of operator nodes and operand nodes. The form of an operand is changed by certain phases, but operands generally refer to a declaration of some variable or constant. Each operand also serves as the root of a computation tree which describes the computations necessary to locate the item at runtime. This internal representation is machine independent in that it does not reflect the instruction set, the addressing properties, or the register arrangement of the GE The first four phases of the compiler are also machine independent, since they deal only with this machine independent internal representation.
Figure 1 shows the internal representation of a simple program. The syntactic translator consists of two modules called the lexical analyzer and the parse. The lexical analyzer organizes the input text into groups of tokens which represent a statement. It also creates the source listing file and builds a token table which contains the source representation of all tokens in the source program.
A token is an identifier, a constant, an operator or a delimiter. The lexical analyzer is called by the parse each time the parse wants a new statement. The lexical analyzer is an approximation to a finite state machine. Since the lexical analyzer must produce output as well as recognize tokens, action codes are attached to the state transitions of the finite state machine. These action codes result in the concatenation of individual characters from the output until a recognized token is formed.
Constants are not converted to their internal format by the lexical analyzer. They are converted by the semantic translator to a format which depends on the context in which the constant appears. The token table produced by the lexical analyzer contains a single entry for each unique token in the source program.
Searching of the token table is done utilizing a hash coded scheme which provides quick access to the table. Each token table entry contains a pointer which may eventually point to a declaration of the token.
For each statement, the lexical analyzer builds a vector of pointers to the tokens which were found in the statement. This vector serves as the input to the parse. Figure 2 shows a simple example of lexical analysis. The parse consists of a set of possibly recursive procedures, each of which corresponds to a syntactic unit of the language. These procedures are organized to perform a top down analysis of the source program.
As each component of the program is recognized, it is transformed into an appropriate internal representation. The completed internal representation is a program tree which reflects the relationships between all of the components of the original source program. Figure 3 shows the results of the parse of a simple program. Syntactic contexts which yield declarative information are recognized by the parse, and this information is passed to a module called the context recorder which constructs a data base containing this information.
Declare statements are parsed into partial symbol table nodes which represent declarations. The top down method of syntactic analysis is used because of its simplicity and flexibility. The use of a simple statement recognition algorithm made it possible to eliminate all backup.
The statement recognizer identifies the type of each statement before the parse of that statement is attempted. If a statement is not recognized as an assignment, its leading token is matched against a keyword list to determine the statement type.
This algorithm is very efficient and is able to positively identify all legal statements without requiring keywords to be reserved. Two modules, the context processor and the declaration processor, process declarative information gathered by the parse. The context processor scans the data base containing contextually derived attributes produced during the parse by the context recorder. It either augments the partial symbol table created from declare statements or creates new declarations having the same format as those derived from declare statements.
This activity creates contextual and implicit declarations. The declaration processor develops sufficient information about the variables of the program so that they may be allocated storage, initialized and accessed by the program's operators. It is organized to perform three major functions: the preparation of accessing code, the computation of each variable's storage requirements, and the creation of initialization code. The declaration processor is relatively machine independent.
All machine dependent characteristics, such as the number of bits per word and the alignment requirements of data types, are contained in a table. All computations or statements produced by the declaration processor have the same internal representation as source language expressions or statements. Later phases of the compiler do not distinguish between them. A based declaration of the form. Multiple instances of data having the characteristics of A can be referenced through the use of unique pointers, i.
The declaration processor implements a number of language features by transforming them into suitable based declarations. Automatic data whose size is variable is transformed into a based declaration. For example the declaration:.
Either or both offsets may be zero. The term "word" is understood to refer to the addressable unit of a computer's storage. The address of A consists of a pointer to the declaring block's automatic storage, a word offset within that automatic storage and a zero bit offset.
The word offset may include the distance from the origin of the item's storage class, as was the case with the first example, or it may be only the distance from the level-one containing structure, as it was in the last example. The term "level-one" refers to all variables which are not contained within structures. The declaration processor constructs offset expressions which represent the distance between an element of a structure and the data origin of its level-one containing structure.
If an offset expression contains only constant terms, it is evaluated by the declaration processor and results in a constant addressing offset. If the offset expression contains variable terms, the expression results in the generation of accessing instructions in the object program. The discussion which follows describes the efficient creation of these offset expressions.
The declaration processor suppresses the creation of unnecessary conversion functions c k and boundary functions b k by keeping track of the current units and boundary as it builds the expression.
As a result the offset expressions of the previous example do not contain conversion functions and boundary functions for A and B. During the construction of the offset expression, the declaration processor separates the constant and variable terms so that the addition of constant terms is done by the compiler rather than by accessing code in the object program. The following example demonstrates the improvement gained by this technique.
The word offset and the bit offset are developed separately. Within each offset, the constant and variable parts are separated. These separations result in the minimization of additions and unit conversions.
If the declaration contains only constant sizes, the resulting offsets are constant. If the declaration contains expressions, then the offsets are expressions containing the minimum number of terms and conversion factors. The development of size and offset expressions at compile time enables the object program to access data without the use of data descriptors or "dope vectors. Unless these descriptors are implemented by hardware, their use results in rather inefficient object code.
This code is generally more efficient than code which uses descriptors. In general, the offset expressions constructed by the declaration processor remain unchanged until code generation. Each subscripted reference or sub-string reference is a reference to a unique sub-datum within the declared datum and, therefore, requires a unique offset.
The semantic translator constructs these unique offsets using the subscripts from the reference and the offset prepared by the declaration processor. The declaration processor does not allocate storage for most classes of data, but it does determine the amount of storage needed by each variable. Variables are allocated within some segment of storage by the code generator.
Storage allocation is delayed because, during semantic translation and optimization, additional declarations of constants and compiler created variables are made. The declaration processor creates statements in the prologue of the declaring block which will initialize automatic data.
It generates DO statements, IF statements and assignment statements to accomplish the required initialization. The expansion of the initial attribute for based and controlled data is identical to that for automatic data except that the required statements are inserted into the program at the point of allocation rather than in the prologue.
Since array bounds and string sizes of static data are required by the language to be constant, and since all values of the initial attribute of static data must be constant, the compiler is able to initialize the static data at compi1c time.
The initialization is done by the code generator at the time it allocates the static data. The semantic translator transforms the internal representation so that it reflects the attributes semantics of the declared variables without reflecting the properties of the object machine.
It makes a single scan over the internal representation of the program. A compiler, which had no equivalent of the optimizer phase and which did not separate the machine dependencies into a separate phase, could conceivably produce object code during this scan. The semantic translator consists of a set of recursive procedures which walk through the program tree.
The actions taken by these procedures are described by the general terms: operator transformation and operand processing. Operator transformation includes the creation of an explicit representation of each operator's result and the generation of conversion operators for those operands which require conversion. Operand processing determines the attributes, size and offsets of each operator's operands.
The meaning of an operator is determined by the attributes of its operands. This meaning specifies which conversions must be performed on the operands, and it decides the attributes of the operator's result. An operator's result is represented in the program tree by a temporary node. Temporary nodes are a further qualification of the original operator. For example, an add operator whose result is fixed-point is a distinct operation from an add operator whose result is floating-point.
There is no storage associated with temporaries--they are allocated either core or register storage by the code generator.
A temporary's size is a function of the operator's meaning and the sizes of the operator's operands. A temporary, representing the intermediate result of a string operation, requires an expression to represent its length if any of the string operator's operands have variable lengths.
Operands consist of sub-expressions, references to variables, constants, and references to procedure names or built-in functions. Sub-expression operands are processed by recursive use of operator transformation and operand processing. Operand processing converts constants to a binary format which depends on the context in which the constant was used. References to variables or procedure names are associated with their appropriate declaration by the search function.
After the search function has found the appropriate declaration, the reference may be further processed by the subscriptor or function processor.
Therefore, references to source program variables are placed into a form which contains a pointer to a token table entry rather than to a declaration of the variable. Figure 3 shows the output of the parse. The search function finds the proper declaration for each reference to a source program variable. The effectiveness of the search depends heavily on the structure of the token table and the symbol table. After declaration p. The search function first tries to find a declaration belonging to the block in which the reference occurred.
If it fails to find one, it looks for a declaration in the next containing block. This process is repeated until a declaration is found. Since the number of declarations on the list is usually one, the search is quite fast.
In its attempt to find the appropriate declaration, the search function obeys the language rules regarding structure qualification. It also collects any subscripts used in the reference and places them into a subscript list.
Depending on the attributes of the referenced item, the subscript list serves as input to the function processor or subscriptor. The declaration processor creates offset expressions and size expressions for all variables. These expressions, known as accessing expressions, are rooted in a reference node which is attached to a symbol table node. The reference node contains all information necessary to access the data at run time. The search function translates a source reference into a pointer to this reference node.
See Figure 5. Since each subscripted reference is unique, its offset expression is unique. To reflect this in the internal representation, the subscriptor creates a unique reference node for each subscripted reference. See Figure 6. The following discussion shows the relationship between the declared array bounds, the element size, the array offset and subscripts. The virtual origin is the offset obtained by setting the subscripts equal to zero. It serves as a convenient base from which to compute the offset of any array elements.
During the construction of all expressions, the constant terms are separated from the variable terms and all constant operations are performed by the compiler. Since the virtual origin and the multipliers are common to all references, they are constructed by the declaration processor and are repeatedly used by the subscriptor. The declaration:. Array parameters which may correspond to an array cross section argument must receive their multipliers from an argument descriptor.
Since the arrangement of the cross section elements in storage is not known to the called program, it cannot construct its own multipliers and must use multipliers prepared by the calling program. An operand which is a reference to a procedure is expanded by the function processor into a call operator and possible conversion operators.
Built-in function references result in new operators or are translated. The declaration processor chains together all members of a generic family and the function processor selects the appropriate member of the family by matching the arguments used in the reference with the declared argument requirements of each member. When the appropriate member is found, the original reference is replaced by a reference to the selected.
The function processor determines which arguments may possibly correspond to a parameter whose size or array bounds are not specified in the called procedure. In this case, the argument list is augmented to include the missing size information.
A more detailed description of this issue is given later in the discussion of object code strategies. It is a three argument function which allows a reference to be made to a portion of a string variable, i.
This function is similar to an array element reference in the sense that they both determine the offsets of the reference. As is the case in all compiler operations on the offset expressions, the constant and variable terms are separated to minimize the object code necessary to access the data.
The compiler is designed to produce relatively fast object code without the aid of an optimizing phase. Normal execution of the compiler will by-pass the optimizer, but if extensively optimized object code is desired, the user may set a compiler command option which will execute the optimizer. The optimizer consists of a set of procedures which perform two major optimizations: common sub-expression removal and removal of computations from loops.
The data bases necessary for these optimizations are constructed by the parse and the semantic translator. These data bases consist of a cross-reference structure of statement labels and a tree structure representing the DO groups of each block. Both optimizations are done on a block basis using these two data bases. Although the optimizer phase was not implemented at the time this paper was written, all data bases required by the optimizer are constructed by previous phases of the compiler and the abnormality of all variables is properly determined.
Because of the difficulty of determining the abnormality of a program's variables, the optimization of those programs which may be optimized requires a rather intelligent compiler. A variable is abnormal in some block if its value can be altered without an explicit indication of that fact present in that block. Future revisions to the language definition may help solve the optimization problem.
The code generator is the machine dependent portion of the compiler. It performs two major functions: it allocates data into Multics segments and it generates machine instructions from the internal representation. A module of the code generator called the storage allocator scans the symbol table allocating stack storage for constant size automatic data, and linkage segment storage for internal static data. For each external name the storage allocator creates a link an out-reference or a definition an entry point in the linkage segment.
All internal static data is initialized as its storage is allocated. Due to the dynamic linking and loading characteristics of the Multics environment, the allocation and initialization of external static storage is rather unusual.
The compiler creates a special type of link which causes the linker module of the operating system to create and initialize the external data upon first reference. Therefore, if two programs contain references to the same item of external data, the first one to reference that data will allocate and initialize it. The code generator scans the internal representation transforming it into machine instructions which it outputs into the text segment.
During this scan the code generator allocates storage for temporaries, and maintains a history of the contents of index registers to prevent excessive loading and storing of index values.
Code generation consists of three distinct activities: address computation, operator selection and macro expansion. Address computation is the process of transforming the offset expressions of a reference node into a machine address or an instruction sequence which leads to a machine address.
Operator selection is the translation of operators into n-operand macros which reflect the properties of the machine. A one-to-one relationship often exists between the macros and instructions but many operations load long string, etc.
All macros are expanded in actual code by the macro expander which uses a code pattern table macro skeletons to select the specific instruction sequences for each macro. The length of the object program is minimized by the extensive use of out-of-line code sequences.
Although the compiled code makes heavy use of out-of-line code sequences, the compiled code is not in any respect interpretive. The object code produce for each operator is very highly tailored to the specific attributes of that operator. All out-of-line sequences are contained in a single "operator" segment which is shared by all users. If you can't find a particular language in this list, check up the miscellaneous category.
Numerous compilers, interpreters from different computer programming languages are dumped there. If you are looking for a printed book for a particular programming language, you might want to search Amazon.
If you still can't find it, try the main Free Compilers and Interpreters index. There may be a separate page for it that I forgot to list here. The free Smalltalk implementations have been moved to their own page, since there were just too many to cram into this miscellaneous page. Please see the Free Smalltalk Compilers and Interpreters instead.
It comes with a linker and samples. It is apparently free if you use it for non-commercial purposes. Update : the site originally linked to here appears to have disappeared, and I can't find an official replacement. I suppose you can always search for it, but there's no guarantee that the sites you find are legitimate.
I prefer to list only official sites. It was originally derived from SmartEiffel. The compiler is primarily distributed in source form, although you may be able to get binaries for it from their "apt" repository if you use Debian or Ubuntu Linux.
For those not familiar with Eiffel, it is an object-oriented programming language. It does not have a runtime garbage collector, but manages its memory and resources using a resource acquisition is initialization RAII convention with optional reference counting. The Go programming language, created by Robert Griesemer, Rob Pike, and Ken Thompson, is a language designed to be suitable for modern systems programming and fast compilation and linking. It incorporates built-in support for concurrent programming with processes that can communicate with each other and garbage collection.
Note that due to a name collision with an earlier programming language called Go! Another thing to note before you rush to write your critical systems with it is that the language appears to be still under development.
R is a language and environment for statistical computing and graphics. It is similar to the S language and environment, and some of the code written for S can run unaltered for R although not all - there are differences. Modified 2 years, 11 months ago. Viewed 4k times.
Community Bot 1 1 1 silver badge. Max G. I have developed lot of sytem applications as I worked in a major american grain company. I will be glad to exchange with people who really liked this language. Add a comment. Sorted by: Reset to default. Highest score default Trending recent votes count more Date modified newest first Date created oldest first.
Lisa Ready Lisa Ready 31 1 1 bronze badge. I think one should look elsewhere :D — oligofren.
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