Posts
Q:How do I determine amount of memory currently available for allocating?
A: We can use function coreleft( ) to get the amount of memory available for allocation. However, this function does not give an exact amount of unused memory. If, we are using a small memory model, coreleft( ) returns the amount of unused memory between the top of the heap and stack. If we are using a larger model, this function returns the amount of memory between the highest allocated memory and the end of conventional memory. The function returns amount of memory in terms of bytes.
Q:How does a C program come to know about command line arguments?
A: When we execute our C program, operating system loads the program into memory. In case of DOS, it first loads 256 bytes into memory, called program segment prefix. This contains file tables,environment segment, and command line information. When we compile the C program the compiler inserts additional code that parses the command, assigning it to the argv array, making the arguments easily accessible within our C program.
Q:What is environment and how do I get environment for a specific entry?
A: While working in DOS, it stores information in a memory region called environment. In this region we can place configuration settings such as command path, system prompt, etc. Sometimes in a program we need to access the information contained in environment. The function getenv( ) can be used when we want to access environment for a specific entry. Following program demonstrates the use of this function.
#include
main( )
{
char *path = NULL ;
path = getenv ( "PATH" ) ;
if ( *path != NULL )
printf ( "\nPath: %s", path ) ;
else
printf ( "\nPath is not set" ) ;
}
Q:How do I display current date in the format given below?
Saturday October 12, 2002
A: Following program illustrates how we can display date in above given format.
#include
main( )
{
struct tm *curtime ;
time_t dtime ;
char str[30] ;
time ( &dtime ) ;
curtime = localtime ( &dtime ) ;
strftime ( str, 30, "%A %B %d, %Y", curtime ) ;
printf ( "\n%s", str ) ;
}
Here we have called time( ) function which returns current time. This time is returned in terms of seconds, elapsed since 00:00:00 GMT, January 1, 1970. To extract the week day, day of month, etc.from this value we need to break down the value to a tm structure. This is done by the function localtime( ). Then we have called strftime( ) function to format the time and store it in a string str.