SIMSCRIPT II.5 Programming Language

SIMSCRIPT II.5 Basic Concepts
The go to statement provides great flexibility in directing the flow of control. However, it can
detract from the clarity of the logic and the readability of the program. Unwisely used, it can multiply
the possible paths through the program, rendering comprehension and testing of the logic unnecessarily
difficult. Structured programming principles suggest that the logic of a program should
be expressed in restricted control flow structures. In particular, the concepts of conditional action
and iteration should be represented using the if and do loop structures.
1.18 The Logical End of a Program
The stop statement is used to terminate a program. Because there may be more than one stop
statement in a program, and control flow may be diverted around any stop statement, it does not
always appear as the last statement of a program listing. The following program segment illustrates
the use of the stop statement in conjunction with an if statement:
if X is zero
print 1 line as follows
ZERO IS AN ILLEGAL VALUE FOR X
stop
otherwise
let Z = Y/X
Note: The stop statement is considered to be an unconditional transfer of control.
1.19 The Physical End of a Program
The last statement in every SIMSCRIPT II.5 program must be end. It signals that the entire source
program has been read. The example programs at the end of this chapter illustrate the use of the
end statement.
1.20 A Note on SIMSCRIPT II.5 Program Form
SIMSCRIPT II.5 programs are composed of sequences of conventionally arranged symbols —
some are standardized key words such as let and read and others are programmer-constructed
variable names and numeric constants. The basic symbolic units recognized by the SIMSCRIPT
II.5 compiler in scanning program statements are names and numbers, the special characters +, -, ',
*, /, **, (, ), ", >,