Page 1 of 31 MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION (Autonomous) (ISO/IEC - 27001 - 2005 Certified) Subject code: 12263 SUMMER – 12 EXAMINATIONS Model Answer Q.1. a) Attempt any THREE of the following: i) List various applications of system software (1 mark for each point, any four points) 1) It increases the productivity of computer which depends upon the effectiveness, efficiency and sophistication of the systems programs. 2) Compilers are system programs that accept people like languages and translate them into machine language. 3) Loaders are system programs that prepare machine language program for execution. 4) Macro processors allow programmers to use abbreviation. 5) Provides efficient management of various resources. 6) It manages multiprocessing, paging, segmentation, resource allocation. 7) Operating system and file systems allow flexible storing and retrieval of information. ii) Distinguish between multiprogramming and multiprocessing (1 mark for each difference) 1) 2) 3) 4) Multiprogramming It is the interlarded execution of two of more processed by a processor without waiting for external event. Multiprogramming loads more than one program in to the memory, so that processor can switch between any of the loaded program. These systems are designed to maximize CPU usage. i.e. Number of processes run on a single processor In these several programmes are running at a time, like windows with many programmes open. Multiprocessing 1) It is the simultaneous execution of two or more processes by a multiprocessor within a single computer system. 2) Multiprocessing involves the execution of multiple concurrent processes in a system instead of processing a single process at any one instant. 3) It means a process is run on multiple processors. So execution speed up is achieved 4) It means that computer can process more than one thing at a time.
Page 2 of 31 MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION (Autonomous) (ISO/IEC - 27001 - 2005 Certified) Subject code: 12263 SUMMER – 12 EXAMINATIONS Model Answer iii) Explain the working of Bucket Sort. (2 marks for explanation, 2 marks for example) The sort involves examine the least significant digit of the keyword first, and the item is then assigned to a bucket uniquely depend on the value of the digit. After all items have been distributed the buckets items are merged in order and then the process is repeated until no more digits are left. A number system of base P requires P buckets. There are serious disadvantages to using it internally on a digital compiler 1) It takes two separate processes, a separation and a merge 2) It requires a lot of extra Storage for the buckets. The average time required for the sort is ( N log P(K) ) where N is the table size, K is the maximum key size & P is the radix of the radix sort. The extra storage required is N P.
Page 3 of 31 MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION (Autonomous) (ISO/IEC - 27001 - 2005 Certified) Subject code: 12263 SUMMER – 12 EXAMINATIONS Model Answer iv) Explain hash and random entry search (1 mark for hash, 3 marks for random entry) Ans. In hash and random entry search the random entry number K generated from the key by methods similar to their used in address calculation. If the K th position s avoid, then the new element is put there; is not then some other call must be found for the insertion. The first problem is the generation of a random number from the key. The four character EBCDIC keywords divide the keywords by the table length N and use the remainder. This scheme works well as long as N and the key size have no common factors. For a given group of in keywords the remainder should be fairly evenly distributed over O---(N-1). Another method is to treat the keyword as a binary fraction and multiply it by another binary fraction. The second problem is the procedure to be followed when the first trial entry result in a filled position. There are a member of methods of resolving this problem. 1) Random entry with replacement: A sequence of random numbers is generated from the keyword from each of these a number between 1 and N is formed and the table is protect at the position. Probing are terminated when a void space is found. Notice that the random numbers generated are independence and it is perfectly possible to probe the same position twice. 2) Random entry without replacement: This is the same as above except that any attempt to prove the same position twice is bypassed. This method holds advantage over the only when proves are expensive e.g. for files on tape or drum. 3) Open addressing: If the first probe gives a position K and that position is filled, then the next location K+1 is probed and so on until a free position is found. If the search runs off the bottom of the table, then it is renewed at the top.
Page 4 of 31 MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION (Autonomous) (ISO/IEC - 27001 - 2005 Certified) Subject code: 12263 SUMMER – 12 EXAMINATIONS Model Answer Q.1. b) Attempt any ONE of the following: i) Describe database required by each pass of loader. (3 marks for pass1 database, 3 marks for pass2 database) Ans. Pass 1 data bases 1) Input object decks 2) Initial program load Address (IPLA) supplied by the programmer on the operating system that specifies the address to load the first segment. 3) A program load address (PLA) counter, used to rap truck of each segments assigned location. 4) A tab, global External symbol table (GEST) that is used to store each external symbol and its corresponding assigned core address. 5) A copy of the input to be used by pass2. This may be stored on an auxiliary storage device, such as magnetic tape, disk on drum, on the original object deck may be reread by loader a second time for pass 2. 1) 2) 3) 4) 5) Pass 2 data bases Copy of object programs inputted to pass 1 Initial Program Load address parameter (IPLA) The Program load address counter (PLA) The Global External symbol table (GEST) prepared by pass 1, containing each symbol and its corresponding absolute address value. An array, the Local External Symbol Array (LESA), which is used to establish a correspondence between the ESD ID numbers, used an ESO and RLD cards and the corresponding External Symbols absolute address value. ii) With neat diagram explain intermediate phase of compiler. (3 marks for diagram, 3 marks for explanation) Ans. The compiler creates an intermediate form of source program. It affords 2 advantages 1) It facilitates optimization of object code. 2) It allows a logical separation between machine independent and machine dependent. One intermediate form is a parse tree. For E.G