AUSTRALIAN THE NATIONAL UNIVERSITY Mid Semester Examination, April 2007 COMP2300 (Introduction to Computer Systems ) Writing Period: 1 hour duration Study Period: 0 minutes duration Permitted Materials: One A4 page with notes on both sides. NO calculator permitted. Questions are NOT equally weighted. This exam will contribute 20% to your nal assessment.
The questions are followed by labelled, framed blank panels into which your answers are to be written. Additional answer panels are provided (at the end of the paper) should you wish to use more space for an answer than is provided in the associated labelled panels. If you use an additional panel, be sure to indicate clearly the question and part to which it refers to. The marking scheme will put a high value on clarity so, as a general guide, it is better to give fewer answers in a clear manner than to outline a greater number in a sketchy, half-answered fashion. The Appendix contains information on the PeANUt instruction set, as well as a table with powers of 2 values in decimal. Please write clearly if we cannot read your writing you may lose marks!
Name (family name rst):
Student Number:
Ofcial use only: Q1 (13) Q2 (17)
Total (30)
COMP2300
Mid Semester Exam, April 2007
Page 1 of 10
QUESTION 1 [13 marks]
(a) Assume memory addresses 0x02000411 to 0x02000415 contain the following 8-bit binary values: Address 0x02000411 0x02000412 0x02000413 0x02000414 0x02000415 Binary value 00100010 10001101 11001000 01100011 00110000 Assume sizeof(x) = 2 and sizeof(y) = 2, &x = 0x02000412 and &y = 0x02000414, and the data storage is big endian. (i) What would be printed by the following C statement? printf("Values for x+y: %x %o", x+y, x+y); Clearly show how you derive your answers. QUESTION 1(a)[i]
[2 marks]
(ii) What would be printed by the following C statement? printf("Values for x+y: %d %u", x+y, x+y); Clearly show how you derive your answers. QUESTION 1(a)[ii]
[2 marks]
COMP2300
Mid Semester Exam, April 2007
Page 2 of 10
Question 1 (continued)
Student Number: ................................
(b) The IEEE single-precision oating-point standard is: 1 bit sign, 8 bits exponent with a bias of 127, and the remaining 23 bits are the mantissa (with an implicit leading bit). To four decimal digits, what oating point number is represented by the following 32-bit number (given in hexadecimal representation): 0xC1B80000 QUESTION 1(b) [2 marks]
(c) Consider the following C code: char c1 =0; unsigned char c2 =0; while (1) { c1 ++; c2 ++; } Describe the patterns of values of c1 and c2 9in decimal) that would be generated by the iterations of the loop, as it endlessly executes. QUESTION 1(c) [1 mark]
COMP2300
Mid Semester Exam, April 2007
Page 3 of 10
Question 1 (continued)
(d) Name two limitations of oating point arithmetic that might adversely affect the accuracy of any numerical calculations carried out with it. What is the underlying reason that is common to both these limitations and the phenomenon associated with the integer arithmetic illustrated in Question 1(c)? QUESTION 1(d) [2 marks]
(e) Briey describe the functions of the main components of the Central Processing Unit (CPU) of a typical computer. QUESTION 1(e) [2 marks]
(f) State Moores Law. Briey describe its impact on computer technology over the last 50 years. QUESTION 1(f) [2 marks]
COMP2300
Mid Semester Exam, April 2007
Page 4 of 10
Student Number: QUESTION ................................ 2 [17 marks]
(a) The following program manipulates character strings from the standard C library. # include < stdio .h > # include < string.h > int main (){ char str1 [100] = " computer "; char str2 [100] = " systems"; char * str3 ; str3 = strcat( str1 , str2 ); printf(" str1 ( length =%2 d) is : %s\n" , strlen( str1 ), str1 ); printf(" str2 ( length =%2 d) is : %s\n" , strlen( str2 ), str2 ); printf(" str3 ( length =%2 d) is : %s\n" , strlen( str3 ), str3 ); return 0; } Relevant details of strlen() and strcat() functions are: int strlen( const char *s ); // returns the length of the string s , // not including the terminating \0 character
char * strcat( char * dest , const char * src ); // appends the src string to the dest string , overwriting the // \0 character at the end of dest , and then adds a // terminating \0 character . It returns the value of dest (i) Write the output that the program would generate when it is compiled and run. QUESTION 2(a)[i] [2 marks]
COMP2300
Mid Semester Exam, April 2007
Page 5 of 10
Question 2 (continued)
(ii) Write an implementation of the function strcat() as dened above. Your code must not call any other function except strlen(). QUESTION 2(a)[ii] [6 marks]
(b) A C program myprogram.c has its main program function declared as int main (int argc, char *argv[]);. (i) Describe in words the meaning of the declaration char *argv[]. QUESTION 2(b)[i] [1 mark]
(ii) State the signicance of the declaration, in the context when myprogram.c is compiled into an executable program, i.e. with gcc -Wall -o myprogram myprogram.c. QUESTION 2(b)[ii] [2 marks]
COMP2300
Mid Semester Exam, April 2007
Page 6 of 10
Question 2 (continued)
Student Number: ................................
(c) Briey state the purpose of a function prototype (header) and explain how these can support separate compilation of libraries. QUESTION 2(c) [2 marks]
(d) In C, function parameters are passed by value. Explain, in ...