2 as shown in the figure the input to the assembler

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Unformatted text preview: he instruction set, which are used for instructing the system how we want the program to be assembled inside the computer's memory. For example, there may be pseudo-instructions for telling the system things like: STAR T STAR T SET SET PROGRA M DATA AT 0000 ASIDE ASIDE AN ADDRESS FOR FRST AN ADDRESS FOR SCN AT 1000 SET ASIDE D AN ADDRESS FOR ANS R With this feature, a programmer need not keep track of the storage locations of the data and instructions while writing an assembly language program. That is, he/she need not even tell the computer where to place each data item and where to place each instruction of a program. A language, which allows instructions and storage locations to be represented by letters and symbols instead of numbers, is called an assembly language or symbolic language. A program written in an assembly language is called an assembly language program or a symbolic program. Assembler During the discussion of machine language, we saw that a computer can directly execute only machine language programs that use numbers for representing instructions and storage locations. Hence an assembly language program must be converted (translated) into its equivalent machine language program before it can be executed on the computer. This translation is done with the help of a translator program known as an assembler. The assembler of a computer system is a system software, supplied by the computer manufacturer that translates an assembly language program into an equivalent machine language program of the computer. It is so called because in addition to translating an assembly language program into its equivalent machine language program, it also, "assembles" the machine language program in the main memory of the computer and makes it ready for execution. The process of translating an assembly language program into its equivalent machine language program with the use of an assembler is illustrated in Figure 12.2. As shown in the figure, the input to the assembler is the assembly language program (often referred to as a source program) and its output is the mac...
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