In the preceding chapters it had been seen that the usefulness of digital computers is mainly based on their automatic operation. For a single instruction the computer automatically performs many steps of data moving and manipulation. The programmer can write a set of instructions in a symbolic form and the machine translates the symbols into numerical form upon which the computer can operate. What then is the distinction between an automatic program and a machine program which consists of a list of instructions? Actually the difference in automation between machine and automatic programs is only one of degree, while the decisive difference between the two kinds of programs is their orientation, the former being oriented toward the machine and the latter toward the problems to be solved. A program is machine oriented when it is written in the instruction code of a particular machine. The problem—or source-oriented program is written basically in a form which is independent of the machine on which the problem is to be solved. Therefore the different programs might be better distinguished as machine and source programs, instead of machine and automatic programs.
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