COBOL 算術演算

In COBOL, mathematical operations can be performed either using dedicated verbs (ADD, SUBTRACT, MULTIPLY, DIVIDE) or using the generic and expressive COMPUTE statement.

Arithmetic Operations with Formal Verbs

COBOL provides specific textual instructions for each basic arithmetic operation:

1. Addition (ADD)

Adds one or more values to a variable.

ADD WS-NUM-A TO WS-NUM-B.
* Equivalent to: WS-NUM-B = WS-NUM-B + WS-NUM-A

If you want to save the result in a third variable without modifying the addends, use the GIVING clause:

ADD WS-NUM-A TO WS-NUM-B GIVING WS-RESULT.

2. Subtraction (SUBTRACT)

Subtracts one value from another.

SUBTRACT 10 FROM WS-BALANCE.
SUBTRACT WS-TAX FROM WS-SUBTOTAL GIVING WS-TOTAL.

3. Multiplication (MULTIPLY) and Division (DIVIDE)

Multiply and divide values in a similar fashion.

MULTIPLY WS-QTY BY WS-PRICE GIVING WS-TOTAL.
DIVIDE WS-TOTAL BY WS-ITEMS GIVING WS-AVERAGE.

The COMPUTE Statement

For complex mathematical expressions, using individual arithmetic verbs can be long and difficult to read. The COMPUTE statement allows you to use standard mathematical operators (+, -, *, /, ** for exponentiation) similar to modern languages.

COMPUTE WS-TOTAL = (WS-PRICE * WS-QUANTITY) - WS-DISCOUNT.

Try it yourself