`DOEACC NIELIT O Level A1 R4 January 2010 Part Two Question Answer Sample Model Paper Solutions

DOEACC NIELIT O Level A1 R4 January 2010 Part Two Question Answer Sample Model Paper Solutions. O Level IT Tools and Business System M1 R4 A1 R4 Previous Year Question With Answer Solutions January 2010.

PART TWO SOLUTIONS (O Level January 2010)

Ans. 5(a)

FUNCTIONAL UNITS OF A COMPUTER SYSTEM:

CENTRAL PROCESSING UNIT: The brain of a computer system is the central processing unit (CPU). The CPU processes data transferred to it from one of the various input devices. It then transfers either an intermediate or final result of the CPU to one or more output devices. A central control section and work areas are required to perform calculations or manipulate data. The CPU is the computing center of the system. It consists of a control section. An arithmetic-logic section (fig. 3-1), and an internal storage section (main memory). Each section within the CPU serves a specific function and has particular  relationship with the other sections within the CPU.

CONTROL SECTION: The control section directs the flow of traffic (operations) and data. It also mainatins order within the computer. The flow of control is indicated by dotted arrows in figure. The control section selects one program statement at time from the program storage area, inter-prets the statement, and sends the appropriate electronic impulses to the arihmetic-logic and stor age sections so they can cary out the instructions. The control section does not perform actual processing operations on the data. The control section instructs the input device on when to start and stop transferring data to the input storage area. It also tells the output device when to start and stop receiving data from the output storage area.

ARITHMETIC-LOGIC SECTION: The arithmetic-logic section performs arithmetic operations, such as addition, subtraction. Multiplication, and division. Through internal logic capability, it tests various conditions encountered during processing and takes action based on the result. As indicated by the solid arrows in figure, data flows between the arithmetic-logic section and the internal storage section during processing Specifically, data is transferred as needed from the storage section to the arithmetic-logic section, processed, and returned to internal storage. At no time does processing take place in the storage section. Data maybe transferred back and forth between these two sections several times before processing is completed. The results are then transferred from internal storage to an output device, as indicated by the solid arrow in figure.

INTERNAL STORAGE SECTION: The internal storage section is sometimes called primary storage, main storage, or main memory, because this section functions similar to our own human memory. The storage section serves four purposes: three relate to retention (holding) of data during processing. First as indicated by the solid arrow, data is transferred from an input device to the INPUT STORAGE AREA where it remains until the comptuer is ready to prcess it. Second. A WORKING STORAGE AREA (“scratch pad” memory) within the storage section holds both the data being processed and the intermediate results of the arithmetic-logic operations Third, the storage section retains the processing results in the OUTPUT STORAGE AREA. From there the processing results can be transferred to an output device. The fourth storage section. The PROGRAM STORAGE AREA. Contains the program statments transferred from an input device to process the data. Please note that the four areas (input, working storage, output, and program storage) are not fixed in size or location but are determined by individual program requirement.

Ans. 5(b)

Cache memory: Cache memory is random a ccess memory (RAM) that a computer microprocessor processes data. It looks first in the cahe memory and if finds the looks first in the cahe memory and iffinds the adata there (from a previous reading o data), it does not have to do the more time-consuming reading of data from larger memory.

Cache memory is sometimes described in levels of coloseness and accessibility to the microprocessor. An L1 cche is on the same chip as the microprocessor. (For example, the PowerPC 601 processor has a 32 kilobyte level-1 cache built into its chip.) 1.2 is usually a separate static RAM (SRAM) chip.