C Language (gcc)
Generally the language code will make use of it like bison or lemon parser generator tools. it allows to change error message by custom line number.
#line 50 user.c
by the absence of the file name, current file is taken
Compile C program with -g option as
gcc -g test.c
b 1 => set break point at line no 1
b main => set break point at main function
next => run the program line by line
When you are using 64 bit version of Linux OS, All the software are by default work in 64 bIt Mode.
In the 64 bit Mode the Integral(integer) part only extended but floating point numbers remains constant more info .
long datatype holds 8 byte. The Data size is defined by Application Binary Interface (ABI),More info http://www.x86-64.org/documentation/abi.pdf
Sample C program: