Tutorial 7. Number Colour Black Brown Red Orange Yellow Green Blue Violet Gray White

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1 Tutorial 7 Question 1. Write a C program which declares an array of 20 integers, and initialises them such that the first value is 1, the second 2, and so on, with the last value being 20. Use a loop to do this, rather than assigning the values during the variable declaration. Print the array to the screen to verify it is correct, in the form: { 1, 2, 3, 4,, 20. Question 2 Using the array created and initialised in Question 1, write a program which creates a new array, also 20 elements in size. In this array, store the cumulative sum of the first array. For example, the cumulative sum of the array { 1, 2, 3, 4, 5 is { 1, 3, 6, 10, 15. Print this array to the screen in same format as above. Question 3 Questions 1 and 2 both require an array of integers to be displayed to the screen. Write a function called print_array that performs this task for an array of any size. Ensure that the braces are displayed correctly. Hint: Your function will require both the array and its size as parameters. Modify Question 2 above to make use of this function rather than printing directly to the screen. Question 4 Write a program that will accept as input a number between 0 and 9, and display the appropriate resistor colour code (shown below). Use an appropriate array structure to store these strings, and ensure that invalid inputs (negative or greater than 10) are handled appropriately. Number Colour Black Brown Red Orange Yellow Green Blue Violet Gray White Question 5 Write a program which reads strings from the keyboard and displays them to the screen, one per line. This should continue until the word "quit" is entered by the user. Question 6 Write a program to perform the opposite task of that of Question 4. It should accept as input a string representing the colour of the resistor, and output the appropriate number. Remember that strings cannot be compared using ==! Question 7 Write a program that will echo the characters as they are typed in from the keyboard using getchar(). The program should leave once the. (period or full stop) has been pressed. Challenge Question Extend the functionality of Question 6 such that your program read four colours from the user, and prints out the value of the resistor in Ohms. Assume that you are dealing with 5 band resistors, however the precision field should be ignored, so the user should enter only four colours. You should consider using a module in this program.

2 Tutorial 7 ANSWERS Question 1 int array[20] ; int i ; array[i] = i+1 ; printf ( "{" ) ; if ( i!= 0 ){ printf ( "," ) ; printf ( " %d", array[i] ) ; printf ( " " ) ;

3 Question 2 int array[20] ; int cumulative[20] ; int i, sum ; array[i] = i+1 ; printf ( "{" ) ; if ( i!= 0 ){ printf ( "," ) ; printf ( " %d", array[i] ) ; printf ( " " ) ; sum = 0 ; sum += array[i] ; cumulative[i] = sum ; printf ( "{" ) ; if ( i!= 0 ){ printf ( "," ) ; printf ( " %d", cumulative[i] ) ; printf ( " " ) ;

4 Question 3 int print_array ( int ar[], int size ){ int i ; printf ( "{" ) ; if ( i!= 0 ){ printf ( "," ) ; printf ( " %d", ar[i] ) ; printf ( " " ) ; int array[20] ; int cumulative[20] ; int i, sum ; array[i] = i+1 ; print_array ( array, 20 ) ; sum = 0 ; sum += array[i] ; cumulative[i] = sum ; print_array ( array, 20 ) ;

5 Question 4 char colours[][20] = { "Black", "Brown", "Red", "Orange", "Yellow", "Green", "Blue", "Violet", "Gray", "White" ; int num ; /* number to decode into a colour */ /* enter the action */ printf("please enter the number to convert (0-9): ") ; scanf("%i",&num) ; if ( num >= 0 && num <= 9 ){ printf ( "The colour is %s\n", colours[num] ) ; else { printf ( "That is not a valid number!\n" ) ; /* leave program */ return EXIT_SUCCESS ;

6 Question 5 #include <string.h> char str[50] ; do { scanf ( "%s", str ) ; printf ( "%s\n", str ) ; while ( strcmp ( str, "quit" )!= 0 ) ;

7 Question 6 #include <string.h> char colour[50] ; char colours[][20] = { "Black", "Brown", "Red", "Orange", "Yellow", "Green", "Blue", "Violet", "Gray", "White" ; int found, i, num ; /* number to decode into a colour */ /* enter the action */ printf("please enter the colour to be converted: ") ; scanf("%s",colour) ; i = 0 ; found = 0 ; while ( i < 10 &&!found ){ if ( strcasecmp ( colour, colours[i] ) == 0 ){ num = i ; found = 1 ; i++ ; if ( found ){ printf ( "The code for that colour is: %d\n", num ) ; else { printf ( "That does not seem to be a valid resistor colour code!\n" ) ; /* leave program */ return EXIT_SUCCESS ;

8 Question 7 int main ( void ){ char let ; /* letter read from keyboard */ printf("please enter the anything from now. quits\n\n ") ; /* read in 1 character at least */ do { let=getchar() ; /* read the keyboard */ printf("%c",let) ; /* echo character read */ while (let!= '.') ; /* keep looping until '.' pressed */ /* leave program */ return EXIT_SUCCESS ;

9 Challenge Question #include <string.h> /* Function to return the value of the given colour (str), or -1 if the colour is not valid */ int colour_code ( char str[] ){ char colours[][20] = { "Black", "Brown", "Red", "Orange", "Yellow", "Green", "Blue", "Violet", "Gray", "White" ; int found, i ; int num = -1 ; /* the default value, will be returned unless a match is found */ i = 0 ; found = 0 ; while ( i < 10 &&!found ){ if ( strcasecmp ( str, colours[i] ) == 0 ){ num = i ; found = 1 ; i++ ; return num ; char colour[50] ; int i, num ; float res_value = 0 ; // start value at 0 printf ( "Please enter the 4 colour bands of the resistor: " ) ; for ( i = 0 ; i < 3 ; i++ ){ scanf ( "%s", colour ) ; num = colour_code ( colour ) ; if ( num == -1 ){ printf ( "%s is not a valid colour\n", colour ) ; return -1 ; else { res_value = res_value*10 + num ; // now do the multiplier band scanf ( "%s", colour ) ; num = colour_code ( colour ) ; if ( num == -1 ){ printf ( "%s is not a valid colour\n", colour ) ; return -1 ; else { for ( i = 0 ; i < num ; i++ ){ res_value *= 10 ;

10 printf ( "The value of that resistor is %f Ohms\n", res_value ) ; /* leave program */ return EXIT_SUCCESS ;