1.10 Limits

The ANSI C standard suggests several environmental limits on the use of the C language. These limits are an effort to define minimal standards for a conforming implementation of a C compiler. For example, the number of significant characters in an identifier is implementation-defined, with a minimum set required by the ANSI C standard.

The standard also includes several numerical limits that restrict the characteristics of integral and floating-point types. For the most part, these limits will not affect your use of the C language or compiler. However, for unusually large or unusually constructed programs, certain limits can be reached. The ANSI standard contains a list of minimum limits, and your platform-specific DEC C documentation contains the actual limits used in DEC C.

1.10.1 Translation Limits

As intended by the ANSI C standard, the DEC C implementation avoids imposing many of the translation limits, allowing applications more flexibility. The DEC C limits are:

A maximum of 32,767 significant characters in an internal identifier or macro name (a warning message is issued if this limit is exceeded)
A maximum of 1023 significant characters in an external identifier for Digital UNIX systems.
A maximum of 31 significant characters in an external identifier for OpenVMS VAX platforms (a warning message is issued if this limit is exceeded and the identifier is truncated)
A maximum of 253 function arguments/formal parameters on OpenVMS systems; a maximum of 1023 function arguments/formal parameters on Digital UNIX systems.
A maximum of 1012 bytes in any one function argument, and a maximum of 1012 bytes in a function argument list on OpenVMS systems
A maximum of 32,767 characters in a logical source line
A maximum of 32,767 characters in a physical source line
A maximum of 32,767 bytes in the representation of a string literal (this limit does not apply to string literals formed as a result of concatenation)

1.10.2 Numerical Limits

Numerical limits define the sizes and characteristics of integral and floating-point types. Numerical limits are described in the limits.h and float.h header files. The limits are:

Each character of type char is represented in 8 bits.
Each character of type wchar_t is represented in 32 bits.
The machine representation and set of possible values for the char type is the same as for the signed char type. A compiler command-line option changes this equivalence to unsigned char .
On OpenVMS systems, the machine representation and set of possible values for the int and signed int types are the same as for the long int type.
On OpenVMS systems, the machine representation and set of possible values for the unsigned int type are the same as for the unsigned long int type.
On Digital UNIX systems, the long int and unsigned long int types are 64 bits, while int and unsigned int are 32 bits.
The machine representation and set of possible values for the long double type is the same as for the double type.

1.10.3 Character Display

Characters from the executable character set are output to the active position on the screen or in a file. The active position is defined by the ANSI C standard as the spot where the next output character will appear. After a character is output, the active position advances to the next position on the current line (to the left or right).

The DEC C compiler moves the active position from left to right across an output line.

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