Simple C program-please explain output.

[hitesh inception]

int main() { int a=7, t=0; t=--a+--a+a+++a; printf("%d",t); }

output: 20

I could not understand why it prints '20' ? please explain it !

[Anand Hariharan]

Do not try to understand code that is meaningless and/or has undefined behaviour.

Look up http://www.c-faq.com -- Section 3. All of it would make good reading, but 3.8, 3.2 and 3.11 would probably be the most relevant for you.

There is a (very) brief explanation by Stroustrup at http://www.stroustrup.com/bs_faq2.html#evaluation-order