1) The earlier days the computers memory is occupied only one program after completion of one program it is possible to execute another program is called uni programming.
2) Whenever one program execution is completed then only second program execution will be started such type of execution is called co operative execution, this execution we are having lot of disadvantages.
a. Most of the times memory will be wasted.
b. CPU utilization will be reduced because only program allow executing at a time.
c. The program queue is developed on the basis co operative execution