Appendix A — Intrinsic function reference

The functions built into FORTRAN 77 (§15.10, Table 5). Most are generic: you call the generic name (e.g. ABS) and the result type follows the argument type. The specific names (e.g. IABS, DABS, CABS) name one type each; only a specific name may be passed as an actual argument, and the type-conversion / MAX / MIN / lexical specifics may not be passed at all.

Throughout: I integer, R real, D double precision, C complex, Ch character, L logical.

Type conversion

Generic	Specifics	Result	Meaning
`INT`	`IFIX` (R→I), `IDINT` (D→I)	I	convert to integer, truncating toward zero
`REAL`	`FLOAT` (I→R), `SNGL` (D→R)	R	convert to real
`DBLE`	—	D	convert to double precision
`CMPLX`	—	C	convert to complex (`CMPLX(x)` → x+0i; `CMPLX(x,y)` → x+yi)
`ICHAR`	—	I	code of a single character
`CHAR`	—	Ch	character with a given code (inverse of `ICHAR`)

Truncation & rounding

Generic	Specifics	Meaning
`AINT`	`DINT`	truncate to a whole number (toward zero), result real/double
`ANINT`	`DNINT`	nearest whole number (round half away from zero), result real/double
`NINT`	`IDNINT`	nearest integer

Arithmetic

Generic	Specifics	Meaning
`ABS`	`IABS`, `DABS`, `CABS`	absolute value (`CABS` is the complex modulus, a real)
`MOD`	`AMOD`, `DMOD`	remainder of `a/b` (sign of the dividend)
`SIGN`	`ISIGN`, `DSIGN`	`\|a\|` with the sign of `b`
`DIM`	`IDIM`, `DDIM`	positive difference: `a−b` if `a>b`, else 0
`DPROD`	—	double-precision product of two reals
`MAX`	`MAX0`,`AMAX1`,`DMAX1`,`AMAX0`,`MAX1`	largest of two or more arguments
`MIN`	`MIN0`,`AMIN1`,`DMIN1`,`AMIN0`,`MIN1`	smallest of two or more arguments

Character

Generic	Meaning
`LEN`	declared length of a character entity (its argument need not be defined)
`INDEX(s, t)`	position of the first occurrence of `t` in `s`, else 0
`LGE`, `LGT`, `LLE`, `LLT`	lexical `≥` / `>` / `≤` / `<` of two strings (logical), by the ASCII collating sequence

Complex

Generic	Meaning
`AIMAG(z)`	imaginary part of `z` (a real)
`CONJG(z)`	complex conjugate of `z`

Square root, exponential, logarithm

Generic	Specifics	Meaning
`SQRT`	`DSQRT`, `CSQRT`	square root
`EXP`	`DEXP`, `CEXP`	e raised to the argument
`LOG`	`ALOG`, `DLOG`, `CLOG`	natural logarithm
`LOG10`	`ALOG10`, `DLOG10`	base-10 logarithm

Trigonometric & hyperbolic (arguments in radians)

Generic	Specifics	Meaning
`SIN`	`DSIN`, `CSIN`	sine
`COS`	`DCOS`, `CCOS`	cosine
`TAN`	`DTAN`	tangent
`ASIN`	`DASIN`	arcsine
`ACOS`	`DACOS`	arccosine
`ATAN`	`DATAN`	arctangent
`ATAN2`	`DATAN2`	arctangent of `y/x`, quadrant-correct
`SINH`	`DSINH`	hyperbolic sine
`COSH`	`DCOSH`	hyperbolic cosine
`TANH`	`DTANH`	hyperbolic tangent

forterp notes. All of the above are implemented with their specified semantics (INT toward zero, NINT round-half-away, MOD/SIGN/DIM, ICHAR/CHAR inverse, INDEX first occurrence, the lexical family on the ASCII collating sequence — Appendix C). An argument for which the result is not mathematically defined (e.g. SQRT of a negative) is non-fatal: it yields a value per the target model (IEEE NaN on NATIVE, a FORTRAN-10 recovery value on PDP10) — see Chapter 6 and Appendix D. forterp also exposes some DEC/FORTRAN-10 library functions beyond Table 5; those are extensions, not part of standard F77.