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Answer to Exercise 3-5, page 64 Solution by Paul Griffiths Write the function itob(n,s,b) that converts the integer n into a base b character representation in the string s . In particular, itob(n,s,16) formats n as a hexadecimal integer in s . /* EX3_5.C ======= Suggested solution to Exercise 3-5 */ #include #include void itob(int n, char s[], int b); void reverse(char s[]); int main(void) { ch..

Answer to Exercise 3-4, page 64 Solution by Paul Griffiths - error spotted by Wayne Lubin and fixed. Wayne Lubin's query involved Paul's discussion of two's complement. The text has now been corrected (by Paul). In a two's complement number representation, our version of itoa does not handle the largest negative number, that is, the value of n equal to -(2 to the power (wordsize - 1)) . Explain ..

Answer to Exercise 3-3, page 63 Solution by Paul Griffiths Write a function expand(s1,s2) that expands shorthand notations like a-z in the string s1 into the equivalent complete list abc...xyz in s2 . Allow for letters of either case and digits, and be prepared to handle cases like a-b-c and a-z0-9 and -a-z . Arrange that a leading or trailing - is taken literally. /* EX3_3.C ======= Suggested s..

Answer to Exercise 3-2, page 60 Solution by Paul Griffiths Write a function escape(s,t) that converts characters like newline and tab into visible escape sequences like \n and \t as it copies the string t to s . Use a switch . Write a function for the other direction as well, converting escape sequences into the real characters. /* EX3_2.C ======= Suggested solution to Exercise 3-2 */ #include v..

Answer to Exercise 3-1, page 58 Solutions by Paul Griffiths Colin Barker and Andrew Tesker Our binary search makes two tests inside the loop, when one would suffice (at the price of more tests outside). Write a version with only one test inside the loop and measure the difference in run-time. Paul Griffiths' solution (krx30100.c): /* Solution by Paul Griffiths (paul@paulgriffiths.demon.co.uk) */..

Answer to Exercise 2-10, page 52 Solution by Bryan Williams Rewrite the function lower, which converts upper case letters to lower case, with a conditional expression instead of if-else . /* Exercise 2-10. Rewrite the function lower, which converts upper case letters to lower case, with a conditional expression instead of if-else. Assumptions : by conditional expression they mean an expression i..

Answer to Exercise 2-9, page 51 Solution by Gregory Pietsch In a two's complement number system, x &= (x-1) deletes the rightmost 1-bit in x . Explain why. Use this observation to write a faster version of bitcount . bitcount is written on p.50 as this: /* bitcount: count 1 bits in x */ int bitcount(unsigned x) { int b; for (b = 0; x != 0; x >>= 1) if (x & 01) b++; return b; } Answer: If x is od..

Answer to Exercise 2-8, page 49 Solutions by Gregory Pietsch and Bob Wightman Write a function rightrot(x,n) that returns the value of the integer x rotated to the right by n bit positions. Greg's Cat 0 solution unsigned rightrot(unsigned x, unsigned n) { while (n > 0) { if ((x & 1) == 1) x = (x >> 1) | ~(~0U >> 1); else x = (x >> 1); n--; } return x; } /* main driver added, in a hurry while tir..

Answer to Exercise 2-7, page 49 Solution by Gregory Pietsch Write a function invert(x,p,n) that returns x with the n bits that begin at position p inverted (i.e., 1 changed into 0 and vice versa), leaving the others unchanged. unsigned invert(unsigned x, int p, int n) { return x ^ (~(~0U

Answer to Exercise 2-6, page 49 Solution by Richard Heathfield Write a function setbits(x,p,n,y) that returns x with the n bits that begin at position p set to the rightmost n bits of y, leaving the other bits unchanged. This one's scary. #include unsigned setbits(unsigned x, int p, int n, unsigned y) { return (x & ((~0