Why use so much macros in programming contest

[Gold Roger]

I am new in programming. And just sat on my first ICPC programming contest in my university.
I have seen some of the codes of prominent contest programmers and have seen that they write 20-30 macro's in their code. Like:

#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define ll long long
......

My question is why contest programmers use so much macros in their code..? What is the benefit of that...?

[Peter87]

They probably have very limited time working on the programs so the time it takes writing code is more precious. Writing pb is a little quicker than writing push_back I guess. This will of course have a big impact on the code quality but they will not use the code after the contest so they probably not care. In a real program you don't want to do it like that because it makes it hard to read the code and over time it's impossible to keep track of what all the shorthands mean, and to avoid that they clash with other names.

[Gold Roger]

Thanks for responding Perter87. I got the idea...