The user is aware of the effects of different applications programs (1) but operating systems are invisible to most users. They lie between applications programs, (2) such as word processing, and the hardware. The supervisor program is the most important. It remains in memory, (3) therefore it is referred tо as resident. Others are called non-resident (4) because they are loaded into memory only when needed. Operating systems manage the computer's resources, (5) such as the central processing unit. (6) In addition, they establish a user interface, and execute and provide services for applications software (7) although input and output operations are invoked by applications programs, they are carried out by the operating system.
I am meeting my mother in the afternoon.
1 c
2 a
3 b
4 b
5 c
6 a
7 b
8 c
9 b
10 a
11 b
12 b
13 a
14 a
15 a
16 a
17 a
18 b
19 c
20 b
After studying I'm hungry as a wolf