MICHAEL J. MEFFORD
Vol. 9, No. 10
Purpose: A five-function calculator (addition, subtraction, multiplication,
division, and modulo functions) that works directly from the DOS
command line prompt.
Format: COMPUTE arithmetic expression
Remarks: COMPUTE accepts decimal numbers only, and the operators in its
arithmetic expression are +, -, *, /, and %. Note that the % symbol
does not stand for percent, but rather designates the module operator,
which returns the remainder of an integer division.
(Example: COMPUTE 8 % 5 returns the value 3, since 5 goes into 8
once with a remainder of 3.) When working on real numbers with a
fractional part the modulo operator in COMPUTE rounds off the
operands before the division.
The standard order of precedence for arithmetic operations is
followed by default. Multiple levels of parentheses and/or square
brackets are supported, however, so that the order in which
calculations are made can be modified. Thus, while COMPUTE 4 + 5 * 2
returns the value 14, the command COMPUTE (4 + 5) * 2 returns 18.
COMPUTE stores its last calculated result within its own .COM file.
This number, designated x, can be recovered and used in the next
calculation, whose result becomes the new x. The value of the
currently-stored x can be seen by entering the command COMPUTE x,
and x can be used as an operand, as in COMPUTE x + 5.
The program can handle decimal numbers up to 20 digits on either side
of the decimal point. Rounding errors are precluded by using a binary
coded decimal (BCD) format. Under DOS 3.x and later, COMPUTE can be
renamed to a shorter name to save keystrokes. Under DOS 2.x, however,
the program cannot be renamed and must be stored either in the current
directory or in one designated in a PATH= statement.