Using intrinsic functions (built-in functions)

Some high-level programming languages have built-in functions that you can reference in your program as if they were variables that have defined attributes and a predetermined value. In COBOL, these functions are called intrinsic functions. They provide capabilities for manipulating strings and numbers.

Because the value of an intrinsic function is derived automatically at the time of reference, you do not need to define functions in the DATA DIVISION. Define only the nonliteral data items that you use as arguments. Figurative constants are not allowed as arguments.

A function-identifier is the combination of the COBOL reserved word FUNCTION followed by a function name (such as Max), followed by any arguments to be used in the evaluation of the function (such as x, y, z). (Optionally, the reserved word FUNCTION may be omitted if the function name is referenced in the REPOSITORY paragraph.) For example, the groups of highlighted words below are function-identifiers:

Unstring Function Upper-case(Name) Delimited By Space
    Into Fname Lname
Compute A = 1 + Function Log10(x)
Compute M = Function Max(x y z)

A function-identifier represents both the invocation of the function and the data value returned by the function. Because it actually represents a data item, you can use a function-identifier in most places in the PROCEDURE DIVISION where a data item that has the attributes of the returned value can be used. You can also use a function-identifier in the ENVIRONMENT DIVISION within the REPOSITORY paragraph.

The COBOL word function is a reserved word, but the function-names are not reserved. You can use them in other contexts, such as for the name of a data item. For example, you could use Sqrt to invoke an intrinsic function and to name a data item in your program:

Working-Storage Section.
01  x                 Pic 99  value 2.
01  y                 Pic 99  value 4.
01  z                 Pic 99  value 0.
01  Sqrt              Pic 99  value 0.
. . .
    Compute Sqrt = 16 ** .5
    Compute z = x + Function Sqrt(y)
    . . .

A function-identifier represents a value that is of one of these types: alphanumeric, national, numeric, or integer. You can include a substring specification (reference modifier) in a function-identifier for alphanumeric or national functions. Numeric intrinsic functions are further classified according to the type of numbers they return.

The functions MAX and MIN can return either type of value depending on the type of arguments you supply.

Functions can reference other functions as arguments provided that the results of the nested functions meet the requirements for the arguments of the outer function. For example, Function Sqrt(5) returns a numeric value. Thus, the three arguments to the MAX function below are all numeric, which is an allowable argument type for this function:

Compute x = Function Max((Function Sqrt(5)) 2.5 3.5)

Related references
REPOSITORY paragraph (Enterprise COBOL for z/OS® Language Reference