Originally, Pakistan was a constitutional monarchy with the British Monarch as head of state. The monarchy was abolished in 1956, and instead of a monarch Pakistan had a figurehead president.
However in 1969 there was a military coup and General Agha Mohammad Yahya Khan had himself declared President. The constitution was revised, and the President ruled Pakistan directly, as a dictator.
In the next decades democracy would be restored, and so would the figurehead presidency, only to again be abolished and replaced with executive-president military rule.
Currently, Pakistan has an executive president, Pervez Musharraf. Musharraf siezed power in a 1999 coup, and has ruled largely as Pakistan's "cheif executive" (as was his original title). However in recent years he has made some power concessions back to the legislature. It remains to be seen if Musharraf will leave office creating a permanent executive presidency for Pakistan, or once again reduce the office to a figurehead.