**Abstract:**
The timetabling is a difficult problem, which is an element of the widen field of Scheduling. The scheduling problems belong to NP hard problems and are defined as an allocation problem of resources over time. The classes or lectures timetabling problem is usually solved by hand and taking several days or weeks of repair after feedback from staff and students in departments. This paper proposed an improved algorithm to solve lectures timetabling problem using genetic algorithm (GA), which has enhanced performance especially because the modification of genetic algorithm behavior. This paper also shows implementation details of timetabling software solution, which employs GA for finding an optimal solution of timetabling problem and generating lectures timetables by using real datasets and constraints from the departments at University of Science and Technology, IBB branch (hinted in the paper as college), Yemen. This software was developed by using C# to program genetic algorithm interface and using SQL Server database to store optimal timetables and college information.

**Keywords:**
Genetic algorithm (GA), scheduling, timetabling, chromosome representation, constraints.