e.g.
int a=3;//-----------------------(1)
and
int a_long_variable_name_used_instead_of_small_one=3;//-------------(2)
For C++,
$ cat name.cpp
int main() {
int a = 74678;
int bcdefghijklmnopqrstuvwxyz = 5664;
}
$ g++ -S name.cpp
$ cat name.s
.file "name.cpp"
.text
.align 2
.globl main
.type main, @function
main:
.LFB2:
pushl %ebp
.LCFI0:
movl %esp, %ebp
.LCFI1:
subl $8, %esp
.LCFI2:
andl $-16, %esp
movl $0, %eax
addl $15, %eax
addl $15, %eax
shrl $4, %eax
sall $4, %eax
subl %eax, %esp
movl $74678, -4(%ebp)
movl $5664, -8(%ebp)
movl $0, %eax
leave
ret
.LFE2:
.size main, .-main
.section .note.GNU-stack,"",@progbits
.ident "GCC: (GNU) 3.4.6 20060404 (Red Hat 3.4.6-11.0.1)"
$
As you can see, neither a
nor bcdefghijklmnopqrstuvwxyz
reflect in the assembler output. So, the length of the variable name does not matter at runtime in terms of memory.
But, variable names are huge contributors to the program design. Some programmers even rely on good naming conventions instead of comments to explain the design of their program.
A relevant quote from Hacker News,
Code should be written so as to completely describe the program's functionality to human readers, and only incidentally to be interpreted by computers. We have a hard time remembering short names for a long time, and we have a hard time looking at long names over and over again in a row. Additionally, short names carry a higher likelihood of collisions (since the search space is smaller), but are easier to "hold onto" for short periods of reading.
Thus, our conventions for naming things should take into consideration the limitations of the human brain. The length of a variable's name should be proportional to the distance between its definition and its use, and inversely proportional to its frequency of use.