Uni-programming involves running one program at a time on a computer system, with the operating system managing the execution of each program sequentially. Under this approach, programs must go through an input/output phase and a computing phase separately. As a result, the CPU is often idle as it waits for I/O operations to complete, leading to poor CPU usage when only one program is in memory. Some disadvantages of uni-programming include no interaction between the user and computer during program execution, no way to prioritize processes, and low CPU utilization.

1. Uni-Programming

2. Batch/Uni-
Programming
The user has to submit a job (written on cards
or tape) to a computer operator.
Then computer operator places a batch of
several jobs on an input device.
Jobs are batched together by type of
languages and requirement.
Then a special program, the monitor, manages
the execution of each program in the batch.

3. Memory Layout
for
Uniprogramming

4. Uni-Programming
P2
P3
P4
P1
I/O
CPU
OS

5. OS
Uni-Programming
0
P1
I/O
CPU
Clock
P2
P3
P4
P1

6. Uni-Programming
1
P1
I/O
CPU
Clock
OS
P2
P3
P4
P1

7. Uni-Programming
2
P1
I/O
CPU
Clock
OS
P2
P3
P4
P1

8. Uni-Programming
3
P1
I/O
CPU
Clock
OS
P2
P3
P4
P1

9. Uni-Programming
4
P1
I/O
CPU
Clock
OS
P2
P3
P4
P1

10. Uni-Programming
5
P1 I/O
CPU
Clock
OS
P2
P3
P4
P1
CPU is
idle

11. Uni-Programming
6
P1 I/O
CPU
Clock
OS
P2
P3
P4
P1
CPU is
idle

12. Uni-Programming
7
P1 I/O
CPU
Clock
OS
P2
P3
P4
P1
CPU is
idle

13. Uni-Programming
8
P1 I/O
CPU
Clock
OS
P2
P3
P4
P1
CPU is
idle

14. Uni-Programming
9
P1 I/O
CPU
Clock
OS
P2
P3
P4
P1
CPU is
idle

15. Uni-Programming
10
P1 I/O
CPU
Clock
OS
P2
P3
P4
P1

16. Uni-Programming
11
P1
I/O
CPU
Clock
OS
P2
P3
P4
P1

17. Uni-Programming
12
P1
I/O
CPU
Clock
OS
P2
P3
P4
P2
P1

18. Uni-Programming
13
P2
I/O
CPU
Clock
OS
P3
P4
P2

19. Uni-Programming
14
P2
I/O
CPU
Clock
OS
P3
P4
P2

20. Uni-Programming
15
P2
I/O
CPU
Clock
OS
P3
P4
P2

21. Uni-Programming
16
P2
P3
I/O
CPU
Clock
OS
P3
P4
P2

22. Uni-Programming
17
P3
I/O
CPU
Clock
OS
P4
P3

23. Uni-Programming
18
P3 I/O
CPU
Clock
OS
P4
P3
CPU is
idle

24. Uni-Programming
19
P3 I/O
CPU
Clock
OS
P4
P3
CPU is
idle

25. Uni-Programming
20
P3 I/O
CPU
Clock
OS
P4
P3
CPU is
idle

26. Uni-Programming
21
P3 I/O
CPU
Clock
OS
P4
P3

27. Uni-Programming
22
P3
I/O
CPU
Clock
OS
P4
P3

28. Uni-Programming
23
P3
P4
I/O
CPU
Clock
OS
P4
P3

29. Uni-Programming
24
P4
I/O
CPU
Clock
OS
P4

30. Uni-Programming
25
P4
I/O
CPU
Clock
OS
P4

31. Uni-Programming
00
P4
I/O
CPU
Clock
OS
P4

32. Uni-programming I/O operations are exceedingly slow
(compared to instruction execution).
A program containing even a very small
number of I/O operations, will spend
most of its time waiting for them.
Hence: poor CPU usage when only one
program is present in memory.

33. Disadvantages
Zero interaction between user
and computer.
No mechanism to prioritize
processes
Poor CPU usage when only one
program is present in memory.