IMACH

This function retrieves machine integer constants that define the arithmetic used by the computer.

Function Return Value

IMACH(1) = Number of bits per integer storage unit.

IMACH(2) = Number of characters per integer storage unit:

Integers are represented in M‑digit, base A form as

 

where σ is the sign and 0 ≤ xk < A, k = 0, …, M.

Then,

IMACH(3) = A, the base.

IMACH(4) = M, the number of base‑A digits.

IMACH(5) = AM – 1, the largest integer.

The machine model assumes that floating‑point numbers are represented in normalized N‑digit base B form as

 

where σ is the sign, 0 < x1 < B, 0 ≤ xk < B, k = 2, …, N and E∃ ≤ E ≤ E∀.

Then,

IMACH(6) = , the base.

IMACH(7) = , the number base-B-digits in single precision.

IMACH(8) = , the smallest single precision exponent.

IMACH(9) = , the largest single precision exponent.

IMACH(10) = , the number base-B-digits in double precision.

IMACH(11) = , the smallest double precision exponent.

IMACH(12) = , largest double precision exponent.

Required Arguments

I — Index of the desired constant. (Input)

FORTRAN 90 Interface

Generic: IMACH (I)

Specific: The specific interface name is IMACH.

FORTRAN 77 Interface

Single: IMACH (I)