EXTERN - external variables in the DPS-8 library.

Many externals are used in the DPS-8 C library. These either begin with an underscore character (_), or contain a period (.) in the first 6 characters of their name. Users should avoid creating names of this form, in order to avoid conflicts with library externals.

Many of the external routines are written in assembler.

Below we list some library externals which may be of use.

int errno;
is set to the error status result of most library functions. Use of the "perror" function will print out the message associated with "errno".
char *_prgnm;
is a string containing the name of the program that is currently executing.
int _tzone;
is the time zone of the installation. It gives the number of minutes to add to GMT to get local Standard Time. The default value is -300 (Eastern Standard Time).
int _isdst;
indicates if the installation is currently on Daylight Savings Time or on Standard Time. Non-zero indicates DST.


Incorrect setting of "_tzone" and/or "_isdst" will not cause "localtime" to return the wrong time (assuming the system time is correctly set to the local current time). However, the function "gmtime" will return an incorrect value.

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