Computer Science and Software Engineering
SEMESTER 2, 2016 EXAMINATIONS
CITS2002 Systems Programming
FAMILY NAME:_____________________________ GIVEN NAMES: ______________________
STUDENT ID: SIGNATURE: ____________________________
This Paper Contains: 6 pages (including title page) Time allowed: 2:00 hours (including reading time)
INSTRUCTIONS:
Answer all 6 questions. Each question is worth 10 marks.
PLEASE NOTE
Examination candidates may only bring authorised materials into the examination room. If a supervisor finds, during the examination, that you have unauthorised material, in whatever form, in the vicinity of your desk or on your person, whether in the examination room or the toilets or en route to/from the toilets, the matter will be reported to the head of school and disciplinary action will normally be taken against you. This action may result in your being deprived of any credit for this examination or even, in some cases, for the whole unit. This will apply regardless of whether the material has been used at the time it is found.
Therefore, any candidate who has brought any unauthorised material whatsoever into the examination room should declare it to the supervisor immediately. Candidates who are uncertain whether any material is authorised should ask the supervisor for clarification.
Supervisors Only – Student left at:
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1) Consider the C99 function isSubset(), whose prototype follows:
bool isSubset(char set1[], int len1, char set2[], int len2);
The function receives two arrays of characters, named set1 and set2, whose lengths are provided by parameters len1 and len2, respectively.
All elements of set1 are guaranteed to be unique, but are not necessarily sorted. The same is also true of the elements of set2.
There is no requirement that len1 and len2 have the same value.
The goal of the function is to determine if set2 is a non-empty subset of set1. Write the function isSubset() in C99.
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2a) Different applications for processing large text documents (such as a book¡¯s chapter) may sometimes prefer a chapter¡¯s text to be available as a single (long) string and, at other times, prefer the chapter to be available as a sequence of sentences. This question requires you to write two functions to perform the conversion between chapters and sentences.
Write a function in C99, named makeSentences(), that converts a chapter into a vector of sentences. The function should match the following prototype:
char **makeSentences(char *chapter, int *nSentences);
The function receives a single string (chapter) that points to the chapter¡¯s text. Assume that all sentences end with a full-stop character (¡¯.¡¯), and that chapter is guaranteed to end with a complete sentence.
The function produces 2 values. The function returns all sentences as a dynamically allocated array of dynamically allocated strings. The number of sentences is returned via the function¡¯s second parameter (nSentences). If any call to dynamically allocate memory fails, the function should return NULL.
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2b) Write a function in C99, named makeChapter(), that converts a vector of sentences into a single string that represents the chapter. The function should match the following prototype:
char *makeChapter(char **sentences, int nSentences);
The function receives a vector of sentences (as might be produced by makeSentences(), above) and converts the sentences into a single dynamically allocated string holding a whole chapter of sentences. When (re)constructing the chapter, ensure that you add a single space after each complete sentence. If any calls to dynamically allocate memory fail, makeChapter() should return NULL.
You should assume that nSentences is always strictly greater than zero, and that sentences contains nSentences elements. Assume also that each string in sentences represents a complete sentence.
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3a) Explain clearly the following state transitions for processes and the reasons for the transitions: 1. from Running to Blocked.
2. from Blocked to Blocked-Suspend.
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3b) Explain clearly the difference between a program and a process. What are the important pieces of information that a multi-processing operating system needs to save during process switching?
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4a) Explain the importance of logical to physical address translation.
Consider a 16-bit computer in which the logical address has a 10-bit offset. Explain clearly, with the aid of a diagram, how the logical to physical address translation is performed for this computer.
What is the maximum number of pages that a process can be allocated in this computer?
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4b) Explain the importance of Direct Memory Access (DMA) for Input/Output management. Explain how DMA works, and explain the term cycle stealing in relation to DMA.
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5a) With reference to a diagram, explain the actions of a Unix-based operating system when a process invokes the fork() system-call.
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5b) Explain clearly how virtual memory helps in improving processor utilization in a multiprogramming system.
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The parameter named dirName points to a character string, providing the name of a directory to be recursively explored for files and subdirectories.
You may assume that dirName, and its subdirectories, contain only files and directories.
After countEntries() has explored everything below the named directory, the parameters nFiles and nDirs should provide, to the calling function, the number of files and directories found, respectively.
If countEntries() finds a directory that cannot be opened, it should report an error and continue its processing (i.e. the function should not exit on such an error).
6) Consider the function countEntries(), whose prototype follows:
void countEntries(char *dirName, int *nFiles, int *nDirs);
Write the function countEntries() in C99.
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