21. Since the experiment can be dangerous, it is important to take precautions against injury.
a) , , .
b) , .
c) , .
d) , .
22. Provided that the results of our survey are positive, we will continue to investigate this issue.
a) , , .
b) , .
c) , .
d) , .
23. To achieve success, it is important to measure and analyze these processes.
a) , .
b) .
c) .
d) , .
24. Had we all the necessary devices, we should be able to test the new equipment.
a) , .
b) , .
c) , .
d) , .
VII. . : T (true), ; F (false), ; N (no information), .
A memory is just like a human brain: it is used to store data and instructions. Computer memory is the storage space in computer where data is to be processed and instructions required for processing are stored. The memory is divided into large number of small parts called cells, each cell has a unique address which varies from zero to memory size minus one. Memory is primarily of three types: Cache memory, Primary (main) memory, Secondary memory.
Cache memory is a very high speed semiconductor memory which can speed up CPU. The parts of data and programs, which are most frequently used, are transferred from disk to cache memory by operating system, from where CPU can access them. The advantages of cache memory are as follows: it is faster than main memory; it consumes less access time as compared to main memory; it stores the program that can be executed within a short period of time; it stores data for temporary use. But there are some disadvantages: it has limited capacity and it is very expensive.
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Primary memory holds only those data and instructions that computer needs for current work. It has limited capacity and data is lost when power is switched off. Primary memory is generally made up of semiconductor device. These memories are not as fast as registers. The data and instruction required to be processed reside in main memory. It is divided into two subcategories RAM and ROM.
Secondary memory is also known as external memory or non-volatile. It is slower than main memory and is used for storing data/information permanently. CPU does not access these memories directly, they are accessed via input-output routines. Contents of secondary memories are first transferred to main memory, and then CPU can access it.
25. Any type of memory is represented by cells, each having its proper address.
26. All three types of memory are non-volatile, i.e. the data is lost when the power is turned off.
27. Primary memory is considered to be the most efficient one.
28. Cache memory is said to be the fastest type of memory.
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