COBOL intrinsic functions

Intrinsic functions arrived with an amendment to COBOL-85 in 1989 (42 of them) and grew with each standard. A function call is an operand: FUNCTION name or FUNCTION name(arg, arg…), used anywhere a value of its kind fits. The viewer colours the name after FUNCTION as a function.

Calling and declaring

       ENVIRONMENT DIVISION.
       CONFIGURATION SECTION.
       REPOSITORY.
           FUNCTION ALL INTRINSIC.
       PROCEDURE DIVISION.
           MOVE FUNCTION UPPER-CASE(NAME) TO OUT-NAME
           COMPUTE R = FUNCTION SQRT(FUNCTION ABS(X)) + FUNCTION PI
           DISPLAY FUNCTION CURRENT-DATE(1:8)
           MOVE FUNCTION MAX(A, B, T(ALL)) TO TOP-VALUE
           DISPLAY FUNCTION TRIM(S TRAILING) "|"
           MOVE FUNCTION WHEN-COMPILED TO STAMP.

A function with no arguments is written without parentheses (FUNCTION PI, FUNCTION CURRENT-DATE); the parentheses may be empty.
Arguments may be items, literals, expressions or other functions. ALL as a subscript passes every element of a table.
The result has a type of its own: numeric, integer, alphanumeric, national. It may be reference-modified: FUNCTION CURRENT-DATE(1:4).
The REPOSITORY paragraph (2002) lists names so that FUNCTION need not be written: FUNCTION ALL INTRINSIC, FUNCTION TRIM INTRINSIC, or FUNCTION my-fn AS "MYFN" for a user-defined function. GnuCOBOL then accepts TRIM(S) alone; IBM does not need or support that shorthand for all names.
User-defined functions are written in a FUNCTION-ID program unit with PROCEDURE DIVISION USING … RETURNING r (Object-oriented COBOL for the unit shapes).

Mathematical

Function	Result	Std
`ABS(n)`	Absolute value	89
`ACOS(n)` `ASIN(n)` `ATAN(n)` `COS(n)` `SIN(n)` `TAN(n)`	Trigonometric functions (radians)	89
`ANNUITY(rate, periods)`	Ratio of an annuity payment to the loan	89
`E`	Euler’s number	89
`EXP(n)` `EXP10(n)`	e to the n; 10 to the n	89; 2002
`FACTORIAL(n)`	n! for integers 0 to 28	89
`FRACTION-PART(n)` `INTEGER-PART(n)` `INTEGER(n)`	Fraction; integer part; greatest integer not above n	89
`LOG(n)` `LOG10(n)`	Natural and common logarithm	89
`MOD(a, b)` `REM(a, b)`	Modulus (sign of b); remainder (sign of a)	89
`PI`	The constant pi	89
`PRESENT-VALUE(rate, v1, v2…)`	Present value of a series of amounts	89
`RANDOM[(seed)]`	Pseudo-random number in [0, 1)	89
`SIGN(n)`	-1, 0 or 1	89
`SQRT(n)`	Square root	89
`HIGHEST-ALGEBRAIC(x)` `LOWEST-ALGEBRAIC(x)`	Largest and smallest value the item can hold	2002

Statistical and ordering

Function	Result
`MAX(a, b…)` `MIN(a, b…)`	Largest and smallest argument (numeric or alphanumeric)
`ORD-MAX(a, b…)` `ORD-MIN(a, b…)`	Position (1-based) of the largest and smallest
`MEAN(…)` `MEDIAN(…)` `MIDRANGE(…)` `RANGE(…)`	Arithmetic mean, median, (max + min) / 2, max - min
`STANDARD-DEVIATION(…)` `VARIANCE(…)` `SUM(…)`	Population standard deviation, variance, total

Strings and characters

Function	Result	Std
`CHAR(n)` `ORD(c)`	The character at ordinal n (1-based) of the collating sequence; the ordinal of a character	89
`CONCATENATE(a, b…)`	The arguments joined	2014; GnuCOBOL earlier
`LENGTH(x)` `BYTE-LENGTH(x)` `LENGTH-AN(x)` `STORED-CHAR-LENGTH(x)`	Length in characters; in bytes; alphanumeric length; length without trailing spaces	89; 2002
`LOWER-CASE(s)` `UPPER-CASE(s)`	Case conversion	89
`REVERSE(s)`	Characters in reverse order	89
`TRIM(s [LEADING \| TRAILING])`	Without leading and trailing spaces	2002
`SUBSTITUTE(s, a1, b1…)` `SUBSTITUTE-CASE`	Replace substrings (case-sensitive and not)	2014
`NUMVAL(s)` `NUMVAL-C(s, sym)` `NUMVAL-F(s)`	Number from text: plain, with currency and separators, floating	89; 2002
`TEST-NUMVAL(s)` `TEST-NUMVAL-C` `TEST-NUMVAL-F`	0 if the text is valid for that `NUMVAL`, else the position of the first bad character	2002
`BOOLEAN-OF-INTEGER(n, len)` `INTEGER-OF-BOOLEAN(b)`	Boolean string from and to an integer	2002
`DISPLAY-OF(n)` `NATIONAL-OF(s)` `CHAR-NATIONAL(n)`	National to alphanumeric and back; national character at ordinal n	2002; IBM
`STANDARD-COMPARE(a, b, …)`	Compare under a standard collating sequence	2014
`BASECONVERT`, `CONVERT` and other 2023 additions	Not described here: I could not read the 2023 function list (see the Not described section of the overview)	2023

Dates and times

Function	Result	Std
`CURRENT-DATE`	21 characters: `YYYYMMDDhhmmsshh` and the offset from GMT (`+hhmm`)	89
`WHEN-COMPILED`	Compile time in the same layout	89
`DATE-OF-INTEGER(n)` `INTEGER-OF-DATE(d)`	Between the integer day number (1 = 1 Jan 1601) and `YYYYMMDD`	89
`DAY-OF-INTEGER(n)` `INTEGER-OF-DAY(d)`	Same for `YYYYDDD`	89
`DATE-TO-YYYYMMDD(d, win, cur)` `DAY-TO-YYYYDDD(d, win, cur)` `YEAR-TO-YYYY(y, win, cur)`	Windows a two-digit year	89 Amend.
`SECONDS-PAST-MIDNIGHT`	Seconds since midnight	2002
`FORMATTED-CURRENT-DATE(fmt)` `FORMATTED-DATE(fmt, n)` `FORMATTED-TIME(fmt, s)` `FORMATTED-DATETIME(fmt, n, s)`	Date or time in an ISO 8601 style format string	2002
`INTEGER-OF-FORMATTED-DATE(fmt, s)` `SECONDS-FROM-FORMATTED-TIME(fmt, s)` `COMBINED-DATETIME(n, s)`	Parse back to numbers; combine	2002
`TEST-DATE-YYYYMMDD(d)` `TEST-DAY-YYYYDDD(d)` `TEST-FORMATTED-DATETIME(fmt, s)`	0 when valid, else the position of the error	2002
`DATEVAL(s, pattern)` `UNDATE(n, pattern)` `YEARWINDOW`	IBM Enterprise COBOL date helpers (a date to an integer for comparison, back, and the century window)	IBM

Locale, exceptions, modules

Function	Result
`CURRENCY-SYMBOL` `MONETARY-DECIMAL-POINT` `MONETARY-THOUSANDS-SEPARATOR` `NUMERIC-DECIMAL-POINT` `NUMERIC-THOUSANDS-SEPARATOR`	Locale symbols (2002)
`LOCALE-COMPARE(a, b)` `LOCALE-DATE(d)` `LOCALE-TIME(t)` `LOCALE-TIME-FROM-SECONDS(n)`	Locale-aware comparison and formatting (2002)
`EXCEPTION-FILE` `EXCEPTION-FILE-N` `EXCEPTION-LOCATION` `EXCEPTION-LOCATION-N` `EXCEPTION-STATEMENT` `EXCEPTION-STATUS`	Describe the last exception (2002)
`MODULE-ID` `MODULE-PATH` `MODULE-SOURCE` `MODULE-CALLER-ID` `MODULE-DATE` `MODULE-FORMATTED-DATE` `MODULE-TIME`	About the running program (GnuCOBOL)
`CONTENT-OF(x)` `CONTENT-LENGTH(x)`	Data and length of a pointer target (GnuCOBOL)

Non-standard routines called with CALL "name" are not functions. GnuCOBOL (CBL_*, C$*, SYSTEM) and Micro Focus have libraries of them for files, directories, screens and arguments; IBM has callable services (CEE*, ILBO*).