SCSP Programming Technique C

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1 Objectives n this chapter, you will learn: To use the arrray data structure to represent lists and tables of values. CHAPTER 1: To define an array, initialize an array and refer to individual elements of an array. ARRAYS To pass arrays to functions. To define and manipulate multidimensional arrays. 1 Muhalim Mohamed Amin Faculty of 2 Contents 1.1 ntroduction An arrays is a group of contiguous memory location consisting of related data items of the same type. 1.1 ntroduction To refer to a particular location or element in the array, we specify the array s name and the position number of it in square brackets ([]). 1.5 Array of Strings The definition : int data[5]; Allocation in memory : 1. Summary First element ntroduction Example 1: int data[5]; Deitel, H.M. and Deitel, P.J (21). C How to Program /E. United State of America: Pearson Education (pg.245) 1.1 ntroduction Size declarator data[] 5 data[1] 15 data[2] data[] 2 data[4] Fifth element ndexes: nteger number. ndex for the first element. Elements Second Third Fourth element element element 25 Named constants are commonly used as size declarators. Name of the arrays const int SZE = 5; int tests[sze]; data int is the data type of the array elements. data is the name of the array. 5 in [5] is the size declarator. t shows the number of This eases program maintenance when the size of the array needs to be changed. elements in the array. The size of an array is (number of elements)*(size of each element) 5 6 1

2 1.1 ntroduction Contents 1.1 ntroduction Size of an array Declaration and definition Accessing element and storing values in arrays The size of an array is the total number of bytes allocated for it. Size = (number of elements) * (byte size of each element) Examples 1: int data[5] with 4 bytes each. Total size = 5 * 4 = 2 bytes 1.5 Array of Strings Examples 2: double data[1] with 8 bytes each. Total size = 1 * 8 = 8 bytes 1. Summary 8 ntroduction (a) Declaration and definition of arrays There are 2 things to do when using arrays: Since an array is a variable, it must be declared and defined before it can be used. a) Declaration and definition of arrays. Parallel arrays Declaration and definition tell the compiler: o b) Accessing elements and storing values in arrays. nitialization nputting values Assigning values Processing values Outputting values o o Syntax: data_type variable_name[n]; // n is number of elements 9 Forouzan, B.A. and Gilberg, R.F (21). Computer Science: A Structured Programming Approach Using C (2/E). United State of America: Brook/Cole.(pg.55) The name of the array The data type of each element The number of elements in the array 1 Forouzan, B.A. and Gilberg, R.F (21). Computer Science: A Structured Programming Approach Using C (2/E). United State of America: Brook/Cole.(pg.54) Examples: Declaring and defining arrays. Parallel arrays int data[]; Two or more arrays with the same number of elements data[] data[1] used for storing related information about a collection of data objects. data[2] Type of each element Example: double x[5]; Name of the array char y[]; int id[num_students]; double gpa[num_students];... y[] y[1] y[2] The arrays id and gpa each have elements. We can store the id and gpa for each student i in id[i] y[2] y[28] y[29] Number of elements Number of elements #define NUM_STUDENTS x[] x[1] x[2] x[] x[4] 11 and gpa[i]. 12 Hanly, J.R and Koffman, E.B. (21). C Program Design for Engineers 2/E. United State of America: Addison Wesley Longman nc. (pg: ) 2

3 (b) Accessing elements and storing values in arrays Example: Declaring and defining parallel arrays. The integer enclosed in brackets is the unique array int id[]; subscript.... id[] id[1] id[2] id[29] ts integer value must be in the range from to (n-1), where n is the number of element in the array. Student 1 Student 2 Student Student Example: The last subscript number for element is (-1) = 29. double gpa[];... gpa[] 1 gpa[1] gpa[2] Hanly, J.R and Koffman, E.B. (21). C Program Design for Engineers 2/E. United State of America: Addison Wesley Longman nc. (pg: ) char y[]; gpa[29]... y[] y[1] y[2] 14 y[2] y[28] y[29] Hanly, J.R and Koffman, E.B. (21). C Program Design for Engineers 2/E. United State of America: Addison Wesley Longman nc. (pg: ) nitialization iii) Partial initialization: Like ordinary variable, arrays may also be initialized using any of these 4 ways. i) Basic initialization: int x[5] =,,12,24,; x[] x[1] x[2] x[] x[4] Forouzan, B.A. and Gilberg, R.F (21). Computer Science: A Structured Programming Approach Using C (2/E). United State of America: Brook/Cole.(pg.56) All filled with s x[] x[1] x[2] x[] x[4] int x[5] = ; 12 iv) nitialization to all zeros: int x[ ] =,,12,24,; ii) nitialization without size: x[] x[1] x[2] x[] x[4] x[] x[1] x[2] x[] x[4] 15 The rest are filled with s int x[5] =,; 16 Forouzan, B.A. and Gilberg, R.F (21). Computer Science: A Structured Programming Approach Using C (2/E). United State of America: Brook/Cole.(pg.56) Default initialization nitialization with a string Global array à all elements initialized to by default. Local array à all elements uninitialized by default. Character array can be initialized by enclosing string in " ": const int SZE = 6; char fname[sze] = Ahmad"; Example: By default: global[5]=,,,, Must leave room for the null character \ at end of array. f initializing character-by-character, must add in \ explicitly: const int SZE = 6; char fname[sze] = A, h, m, a, d,'\'; 1 18

4 Example 1: Example 2: nitialize an array, name with string Ahmad. nitialize an array, name with string Ahmad character-bycharacter. Null character \ marks the end of a string A h m a d \ name[] name[1]name[2]name[]name[4]name[5]name[2]name[]name[4]name[5] Figure: name in the memory after initialization Activity 1.1: Write a C program to display your name as the nputting values 1 The array can be filled by reading the values from the Define the validity of the following arrays definition. f invalid, explain the reason. (a) (b) (c) (d) (e) (f) (g) keyboard or a file. Example: nput of array data for 5 elements. int numbers[l] =,,1,,,1,,,1,1; int matrix[5] = 1,2,,4,5,6,; double radix[1] =.2,4.; int table[] = 2,,,2,,45,9; char codes[] = A,'X,'1,'2,'s'; int blanks[]; char name[1] = Mubassyir ; (value:,,12,24,) (Program_28b.c) Here are the contents of the data array: data[] data[1] data[2] data[] data[4] 22 Coding: nputting values 2 The input value also can be done using a loop. To enter any 5 integer nputs of array data. The most appropriate loop is the for because the number of elements is fixed and known. Example: nput of array data for 5 elements. for (i = ; i < 5; i++) scanf( %d, &data[i]); 2 24 Forouzan, B.A. and Gilberg, R.F (21). Computer Science: A Structured Programming Approach Using C (2/E). United State of America: Brook/Cole.(pg.55) 4

5 Example 1: Using for loop to enter 5 input values into an Example 2: Using for loop to enter 5 input values into a array from the keyboard. parallel array from the keyboard Examples: Assigning values The values can be assigned to individual array element Assigning variable n with value of the first element of an using the assignment operator. data[] data[1] data[2] data[] data[4] Here are the contents of the data array: = = = = = array data. ; data[] + 4; data[] + data[1]; data[2] * 2; pow(data[2],2); 1 int data[] =,,1,2,1; int n; n = data[]; // n = Assigning variable n with value of the sum of second and (Program_28a.c) 2 third element of an array data. int x = 5,n; int data[x] =,,1,2,1; n = data[1] + data[2]; // n = 1 data[] data[1] data[2] data[] data[4] 2 28 match fully in type and size. fourth element. The arrays have to copy at the individual element levels. int data[] =,,1,2,1; data[1] = data[]; // data[1] = 2 Example: int data[5] =,,1,2,; int bonus[5] = 1,2,,4,5; Assigning variable n with value of the last element of an array data. int x = 5,n; int data[x] =,,1,2,1; n = data[x-1]; // n = 1 One array cannot be assigned to another array, even if they Assigning the second element of an array data with the 29 data = bonus; data[] = bonus[4]; // not legal // data[] = 5 5

6 Activity 1.2: Given an array with double type as below. Processing values (a) How to declare the array with the initial values? (b) Explain what will be happened and the output for each statement in the table. Array elements can be treated as ordinary variables of the same type as the array When using ++, -- operators, don t confuse the element Statement x[] x[1] x[2] x[] x[4] Explanation with the subscript: Example: Output x[] = 25.; sum = x[] + x[1]; sum += x[2]; x[] += 1. tests[i]++; // add 1 to tests[i] tests[i++]; // increment i, // no effect on tests x[2] = x[] + x[1]; 1 Hanly, J.R and Koffman, E.B. (21). C Program Design for Engineers 2/E. United State of America: Addison Wesley Longman nc. (pg: ) Activity 1.: 2 Given int y[]=1,14,28,26,2,1,5; int sum =, i = ; Outputting values Another common application is printing the contents of an Assume the statements are execute in sequence. array. (a) Draw the array and label with it subscript contain the initial values. (b) Explain what will be happened and the output for each statement in the table. Statement Explanation printf( %d, data[]); printf( %d, data[1]); printf( %d, data[]); Output This is easily done with a for loop. y[i]++; sum = y[] for (i = ; i < ; i++) printf( %d, data[i]); --y[1]; sum = y[i++] + ; y[i++] -= y[5]; 4 Example 2: To enter any 5 integer nputs of array data. and display all entered values. Forouzan, B.A. and Gilberg, R.F (21). Computer Science: A Structured Programming Approach Using C (2/E). United State of America: Brook/Cole.(pg.58) Example 1: 5 To display the initialized array, name with string Ahmad. 6 6

7 Example : int id[5]; id[] To display all 5 students with their id and gpa entered. id[1] id[2] 161 id[4] Student Student 1 Student 2 Student Student 4 double gpa[5]; gpa[] gpa[1]..99 gpa[2] 4. gpa[4] Figure: id and gpa in the memory. 8 Activity 1.4: Contents Write a C program to display your name as the What is the output of the following code? 1.1 ntroduction Passing individual elements Passing the whole array (You may need to use a calculator.) 1.5 Array of Strings 1. Summary 9 4 ntroduction To pass an array to a function, just use the array name: To process arrays in a large program, we have to be able to pass them to functions. showscores(tests); To define a function that takes an array parameter, use This can be done in two ways: empty [] for array argument: (a) Pass individual elements. // function prototype void showscores(int []); (b) Pass the whole array. // function header void showscores(int tests[]) 41 Forouzan, B.A. and Gilberg, R.F (21). Computer Science: A Structured Programming Approach Using C (2/E). United State of America: Brook/Cole.(pg.55) 42 Forouzan, B.A. and Gilberg, R.F (21). Computer Science: A Structured Programming Approach Using C (2/E). United State of America: Brook/Cole.(pg.55)

8 (a) Pass individual elements When passing an array to a function, it is common to pass They array can be passed as individual elements to a function like any other variable. array size so that function knows how many elements to process: The array element type must matches the function parameter type. showscores(tests, ARRAY_SZE); Array size must also be reflected in prototype, header: Passing the individual element of array to function can be in two forms: Pass by value (pass its contents). // function prototype void showscores(int [], int); e.g. printf ( %d, A[2]); // function header void showscores(int tests[], int size) Pass by reference (pass its addresses). e.g. scanf ( %d, &A[2]); 4 44 int main(void) int i; int base[] =, 4, ; Passing individual element by value. // Program_1b.c void print_square(int *y); Example 2: base[] 4 base[1] base[] return ; void print_square(int y) printf( %d, y * y); y return; Forouzan, B.A. and Gilberg, R.F (21). Computer Science: A Structured Programming Approach Using C (2/E). United State of America: Brook/Cole.(pg.6) Activity 1.5: Tips:. 46 base[] y Requires * deference &base Address (pointer) Forouzan, B.A. and Gilberg, R.F (21). Computer Science: A Structured Programming Approach Using C (2/E). United State of America: Brook/Cole.(pg.6) Passing the whole array to a function can only be done by using pass by reference. t usually passes the address of the first element. Example: Example output: Activity_1.5.c base[1] (b) Pass the whole array Modified program to in display Activity Write a the C program your1.4 namesoasthat the the bill can be calculated in a calculation function without return value (pass individual element) and print from display function. your file as 4 Activity 1.4 program and save 4 Refer Comment in your base[] Address operator & void print_square(int *y) printf( %d, *y * *y); return; for(i = ; i < ; i++) print_square(&base[i]); Prints return ; Type include * int main(void) int i; int base[] =, 4, ; Passing individual element by address. for(i = ; i < ; i++) print_square(base[i]); Prints Forouzan, B.A. and Gilberg, R.F (21). Computer Science: A Structured Programming Approach Using C (2/E). United State of America: Brook/Cole.(pg.6) // Program_1a.c void print_square(int y); Example 1: 48 void main(void) int A[] = 1, 2, ; increase (A); // or, increase (&A[]); void increase(int x[]) x[] += 1; // x[] = 11 x[1] += 2; // x[1] = 22 x[2] += ; // x[2] = 8

9 // Program_2.c void average_square(int y[]); Example 1: Passing the whole element by reference (address). int main(void) int base[] =, 4, ; average_square(base); return ; Activity 1.6: base[] 4 base[1] base[] Prints. y Modified program to in display Activity Write a the C program your1.5 namesoasthat the the bill can be calculated in a calculation function without return value (pass the whole array) and print from display function. Refer Activity 1.5.c Comment in your void average_square(int y[]) int i; double sum = ; Average 24.6 Tips: program and save Example output: your file as Activity_1.6.c i for(i = ; i < ; i++) sum += y[i] * y[i]; printf(" Average %.2f ", sum/); return; sum 49 Forouzan, B.A. and Gilberg, R.F (21). Computer Science: A Structured Programming Approach Using C (2/E). United State of America: Brook/Cole.(pg.64) Contents 5 ntroduction 1.1 ntroduction An array can be defined as a multiple sets of data. A 2-dimensional array can be thought of as a table, which has x number of rows and y number of columns. Use two size declarators in definition: const int ROWS = 4, COLS = ; int exams[rows][cols]; 1.5 Array of Strings 1. Summary First declarator is number of rows; second is number of columns Representation nitialization Example: Basic initialization for an array, data. const int ROW = 2, COLUMN = ; data[row][column] = 1,5,, 92,8,4; [] Figure: A 2-dimensional array with rows and 4 columns. [2] 1 5 [1] To access and assign value to an element in the array, use two subscripts data[][2] = 2; The array a is identified by an element name of the form a[row,column]. 5 [1] [] 54 9

10 Passing function arguments Use array name as argument in function call: getdata(student,); // function call Use empty [] for row, size declarator for column in prototype, header: const int COLUMN = ; // Prototype void getdata(int [][COLUMN], int); Example 1: (without function) To calculate average mark of quizzes taken by each of 5 students. (get the marks from keyboard) // header definition void getdata(int student[][column], int row); Activity 1.: Answer following questions on theas linethe Write athe C program to displaybased your name number of the program in the previous example (page 64). (a) Why does the program need to have if-else statements at lines 24? (b) Why the value of i and j are written as i+1 at line 21 and 45, and j+1 at lines 26 and 1? (c) Why the sum need to be at line 41? (d) What we need to do if we want the statement at line 45 as: printf(" -- Student %d: %.2f \n",i+1,average); 5 Example 2: (with function) To calculate average mark of quizzes taken by each of 5 students. (get the marks from keyboard) Write a C program to display your name as the Write a C program to display your name as the below. The programexample (Program_.c) in previous example (page 64) is modified so that each marks will be entered using enter function, calculate the average with calculate function that return the average value, and print from display function. Assume that we remain the records[stud][quz] as local in the main function. 6 1

11 Write a C program to display your name as the Write a C program to display your name as the Activity 1.8: Tips: Refer. Activity_1.5.c Comment in your program and save Modified program to Activity_1.5.c Write a the C program display your namewith as the the following array that contain the electric usage (kwh) within few months for a group of users. Expected Write a Coutput: program to display your name as the The bill for each month and total should be calculated in a calculation functions without return value (pass the whole array) and print all monthly and total bill for each user from display function. your file as kwh / Months Users Activity_1.8.c Contents 1.5 Arrays of Strings ntroduction 1.1 ntroduction Use a two-dimensional array of characters as an array of strings: const int NAMES =, SZE = 1; char students[names][sze] = Ali", Siti", Ahmad" ; 1.5 Array of Strings Each row contains one string Can use row subscript to reference the string in a particular row: 1. Summary printf( %d, students[i]);

12 1.5 Arrays of Strings 1.5 Arrays of Strings Example 1: To displays the number of days in each month in a year. 6 Activity 1.9: Tips:. Comment in your program and save your file as Activity_1.9.c 1.5 Arrays of Strings 68 Write that define an array strings Writea aprogram C program to display yourofname astothe store your friend s name in this class. nitialize the array with 5 names. Print those names. Contents 1.1 ntroduction n the program, write a function to change any name in the initialized array and reprint the names. void changename(char[][strng_sze], int size); 1.5 Array of Strings 1. Summary 69 ntroduction This type of arrays can have more than two dimensions. Example: Define arrays with any number of dimensions. short rectsolid[2][][5]; double timegrid[][4][][4]; //D //4D (a,b,c) When used as parameter, specify all but 1st dimension in prototype, heading: b c void getrectsolid(short [][][5]); void gettimegrid(double [][4][][4]); a Figure: Example of a three-dimensional array (5 x 4 x ). 1 Forouzan, B.A. and Gilberg, R.F (21). Computer Science: A Structured Programming Approach Using C (2/E). United State of America: Brook/Cole.(pg.4)

13 Activity 1.1: Contents Consider the following diagram of three-dimensional array, table. Answer the questions. y x 99 z (a) How to declare the array with integer type? 1.1 ntroduction (b) Write the statement to access value and 99. (c) How to assign value 4 to x? 1.5 Array of Strings (d) What is the similarity between x, y and z? 1. Summary (e) Add x and y? and store at z. Chapter 9 1. Summary 4 Chapter 9 n this chapter, you have learnt: The C language facilitates a structured and disciplined approach to write a computer program. the arrray data structure to represent lists and tables of values. Always write comments to document the programs and practice coding with a good programming style to define an array, initialize program an array and refer to individual will improve readability. elements of an array. A syntax error is caused when compiler cannot passing arrays to functions innormally a program. recognize a statement. the compiler will issues an error message to help us to locate and fix the manipulation ofthe two-dimensional arrays and briefly incorrect statement. overview on multidimensional arrays. 5 Self-Reviews 6 Self-Review Chapter 9 Exercise 1.1: Answer the following questions. Exercise 1.2: (a) The type of all elements in an array must be the same. (True / False) (b) When an array is defined, C automatically sets the value of its element to zero. (True / False) (c) When an array is passed to a function, C uses pass by address. (True / False) (d) Which of the following array(s) initialization statements is valid? i) int ary4 = 1,2,,4; ii) int ary[] = [1,2,,4]; iii) int ary[4] = 1,2; iv) int ary = [1,2,,4]; v) int ary[] = ; Self-Review Tips:. Refer Activity_1.8.c Comment in your program and save Modified program to Activity_1.8.c Write a the C program display your namewith as the the array value of the electric usage (kwh) for 4 months for a group of users that obtained from keyboard using getreading function. Get and store the user name as well. The bill for each month and total should be calculated in a calculation function without return value (pass the whole array). your file as Exercise_1.2.c Print from display function: all user s name; their monthly and total bill; Forouzan, B.A. and Gilberg, R.F (21). Computer Science: A Structured Programming Approach Using C (2/E). United State of America: Brook/Cole.(pg.41) 8 1

14 Self-Review Write a C program to display your name as the Expected output: 9 14