C Program Reviews 2-12

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1 Program 2: From Pseudo Code to C ICT106 Fundamentals of Computer Systems Topic 12 C Program Reviews 2-12 Initialise linecount and alphacount to zero read a character while (character just read is not end of file indicator) if (character just read is equal to end-of-line character) increment the linecount else if (character just read is alphabetic character (i.e., one of 'A'.. 'Z or one of 'a'.. 'z')) increment alphacount read a character endwhile Display linecount and alphacount ICT 106 _Week 12_06 2 int int linecount = 0, alphacount = 0; char c = ' '; printf("the program reads a sequence of lines of text and counts the\n"); printf("number of lines entered, and the number of alphabetic characters\n"); printf("entered. Use ctrl-z to teminate writing\n"); c = getchar(); // read a character while(c!=eof) { // check for EOF if(c == '\n') { // compare new line character linecount++; // increment linecount else if(((c>='a')&&(c<='z')) // check for alphabet characters ((c>='a')&&(c<='z'))) { alphacount++; // increment alphacount c = getchar(); // read a character printf("the number of line is: %d\n", linecount); printf("the number of characters is %d\n", alphacount); return 0; 1

2 Program 3: Constructing Loops Interchanging For-loop and While-loop For-loop Syntax: for(initial value; condition; assignment) { It is not required to use all three fields. One or even all fields can be empty. E.g. for(i =0; i<200; i++); for(; i<200; i++); // no initialisation for(; i<200; ); // only condition field is used for(;;); // infinite for-loop ICT 106 _Week 12_06 5 For-loop and while-loop (do-while) are interchangeable. E.g. for(i=200; i>-1; i--) i=200; // initial value while(i>-1) { // condition i--; // assigment ICT 106 _Week 12_06 6 int input = 0; int col = 0; // control the number of digits on a row Program 4: Prinf() Format do { printf("enter an integer in the range 1 to 9:\n"); scanf("%d%*c", &input); while((input<=0) (input>=10)); // check valid input while(input>0) { col = input; while(col>0) { // print digits on a row printf("%d",input); col--; printf("\n"); // move to the next row input--; Here is a list of format identifiers used with printf: %d %i Decimal signed integer. %o Octal integer. %x %X Hex integer. %u Unsigned integer. %c Character. %s String. %f double %e %E double. %p pointer. %% No argument expected. ICT 106 _Week 12_06 8 2

3 Field Width By default the width of a field will be the minimum required to hold the data. But you are allowed to specify the field width for your need. E.g. printf( -%4d-, 3); // output: - 4- printf( -%8.2f-, 3.4); // output: The first says you require a total field of 4 characters. The second one says you require a total field of 8 characters, within the 8 characters the last 2 will hold the decimal part. ICT 106 _Week 12_06 9 #define INTEREST_RATE 0.05 #define GROWTH 0.03 // expense growth rate #define TAX_RATE 0.15 #define INIT_DEPOSIT #define INIT_EXPENSE double deposit = INIT_DEPOSIT; double expense = INIT_EXPENSE; double tax=0, interest=0; int i = 0; printf("year=%2d, Interest=%8.2f, Tax=%7.2f, Expense=%9.2f, Deposit=%10.2f\n", i, interest, tax, expense, deposit); for(; i<10; i++) { // calculate interest for this year interest = deposit * INTEREST_RATE; // calculate taxation on the interest tax = interest * TAX_RATE; // calculate new expense expense += expense * GROWTH; // calculate new deposit deposit = deposit + interest - tax - expense; printf("year=%2d, Interest=%8.2f, Tax=%7.2f, Expense=%9.2f, Deposit=%10.2f\n", (i+1), interest, tax, expense, deposit); Program 5: Displaying Hex Numbers char c = 'A'; printf("character ASCII value in decimal ASCII value in hexadecimal\n"); for(; c <= 'Z'; c++) { printf(" %c %d %x\n",c,c,c); ICT 106 _Week 12_

4 Program 6&7: Using C Functions Declare all function that are used in your program before the main function. #include <math.h> double valuey = 0.0, power = 0.0, sum = 0.0; int valuef = 0, i; do { printf("please enter value for Y (1.0 to 2.2)\n"); scanf("%lf", &valuey); while((valuey<1.0)&&(valuey>2.2)); // check valid input for(i=0; i<=6; i++) { valuef = func_f(i); // call function f(x) power = pow((double)valuey, (double)i); // calculate y^x sum += (power / ((double) valuef)); // calculate (y^x) / f(x) int func_f(int); // function prototype ICT 106 _Week 12_06 13 printf("function f(x)=%4d, Power=%6.4lf, Progress sum=%6.4lf\n", valuef, power, sum); This function returns the value: f(x) = 1 if x = 0; and f(x) = x * (x-1) * (x-2) *... * 2 * 1; if x is greater than 1. Program 8: Using Arrays e.g. f(5) = 5*4*3*2*1 = 120. int func_f(int x) { int result=1; if(x<=1) { return (1); // return 1 if x is less than 2 for(; x>1; x--) { result *= x; // perform x * (x-1) * (x-2) *... * 2 return (result); ICT 106 _Week 12_06 16 Arrays can be passed by value or reference. void function(int array[]) { void function(int *array) { Use const keyword to protect any modification of an input array void function(const int array[]) { 4

5 #define LEN 10 void getinput(float[]); float getsmallestnumber(const float[]); float getlargestnumber(const float[]); float calculateaverage(const float[]); void outputoriginalnumbers(const float[]); //Display the average of the inputs. printf("the average of the inputs: %f\n", average); //Display the smallest number. printf("the smallest number: %f\n", smallestnumber); //Display the largest number. printf("the largest number: %f\n", largestnumber); float input[len]; float largestnumber, smallestnumber; float average; getinput(input); smallestnumber = getsmallestnumber(input); largestnumber = getlargestnumber(input); average = calculateaverage(input); outputoriginalnumbers(input); A function that reads in 10 float numbers and returns the input to the called function. void getinput(float input[]) { int i=0; printf("enter 10 float numbers\n"); for(;i<len;i++) { scanf("%f", &input[i]); A function for determining the smallest number of the 10 inputs. float getsmallestnumber(const float input[]) { float smallest = input[0]; int i=1; for(;i<len;i++) { if(smallest>input[i]) { smallest = input[i]; A function for determining the largest number of the 10 inputs. float getlargestnumber(const float input[]) { float largest = input[0]; int i=1; for(;i<len;i++) { if(largest<input[i]) { largest = input[i]; return smallest; return largest; 5

6 A function for calculating the average of the 10 inputs float calculateaverage(const float input[]) { float total = 0; int i; for(i=0;i<len;i++) { total += input[i]; return total; A function for displaying the original 10 inputs. void outputoriginalnumbers(const float input[]) { int i; printf("the orginal 10 inputs are:\n"); for(i=0; i<len; i++) { printf("%f\n", input[i]); Program 9: Binary to Integer Conversion using Addition and Logic Shift #include <string.h> char binary[17]; // to hold up to 16 binary numbers and an enter key long intnum=0; int len, base=1; printf("enter a binary number and the equivalent\n"); printf("integer will be displayed.\n"); scanf("%s", binary); // get the length of the binary string len=strlen(binary)-1; // the for-loop converts a binary number // to integer using summation, e.g. // // binary: // integer: = 31 // for(;len>=0;len--) { // add base to intnum if the bit is '1' // otherwise add 0 intnum += ((binary[len] == '1')?(base):(0)); Program 10: Logical Operators Use Logic-AND (&) to mask off bits. E.g., to mark bit 0 and 4 and clear other bits, we use: = & 17; // 17 = 10001b base = base << 1; // multiple base by 2 printf("the equivalent integer is %d\n", intnum); Use Logic-OR ( ) to set bits. E.g. to set bit 2 and 3 but not to alter other bits, we use: = ; // 12 = 1100b ICT 106 _Week 12_

7 int i; for(i=-56; i<=77; i++) { To test if the decimal satisfies the requirement or not. We first need to mask off bit 5, 3 and 2, which is 44 in decimal. However, since the bit 2 must be zero, the final result therefore is 40 in decimal. if((i&44)==40) { printf("%3d in decimal satisfies the requirement\n", i); Program 11: Using Logic Shift in Multiplication and Division int num; printf("enter a integer and it will\n"); printf("multiply the number by 32 and\n"); printf("divide the same number by 16.\n"); scanf("%d", &num); // shift the number to left 5 times printf("%d multiplies by 32: %d\n", num, num<<5); // shift the number to right 4 times printf("%d divides by 16: %d\n", num, num>>4); Program 12: Integer to Binary Conversion using Logic Operators #define LEN 9 void convert(int); prog12_run() { int num; printf("enter a positive integer.\n"); scanf("%d%*c", &num); printf("an 8bit integer: "); convert(num); ICT 106 _Week 12_06 27 printf("\none\'s complement: "); convert(~num); // one's complement printf("\ntwo\'s complement: "); convert(~num+1); // two's complement printf("\n"); void convert(int integer) { char c[len]; int i, mask=1; for(i=len-2; i>=0; i--) { // to test if the bit is 1 c[i] = (integer&mask)?'1':'0'; // shift the masking bit to left mask = mask << 1; c[len-1] = '\0'; // end of array printf("%s", c); // output binary 7