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Programming Training. Main Points: - C Statements - Problems with selections. - Problems with repetitions. Printf(). printf(“format”, var) EACH VARIABLE REQUIRES A SPECIFICATOR printf(“text %sp <br>”, var1); printf(“text %s1 text %s2 text …<br>”, var1,var2,…);
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Programming Training Main Points: - C Statements - Problems with selections. - Problems with repetitions.
Printf() printf(“format”, var) EACH VARIABLE REQUIRES A SPECIFICATOR printf(“text %sp \n”, var1); printf(“text %s1 text %s2 text …\n”, var1,var2,…); - format specificators: %d, %ld, %f, %lf. - \n special character for newline. Remark: Use \n to jump to a new line.
Scanf() scanf(“format”,&var) EACH VARIABLE REQUIRES A SPECIFICATOR EACH VARIABLE IS PREFIXED BY & scanf(“%sp”,&var); No text or space is allowed Remark: READ ONLY ONE VARIABLE.
Some rules Read a variable var: printf(”var="); scanf("%sp", &var); Write a variable var: printf(”var = %sp \n”,var); Write a text: printf(”My Text \n”); Write a line of start: printf(”\n\n\n******** \n\n\n”); # include <stdio.h> # include <math.h> # include <conio.h> int main(int args, char ** argc) { double a, b, max; printf(”\n***************\n”); printf("a="); scanf("%lf", &a); printf("b="); scanf("%lf", &b); sum = a+b; printf(”sum=%lf \n\n", sum); printf(”\n***************\n”); return 1; }
C Arithmetic Aritmetics operators: • +, -, *, / • ++, -- for incrementing and decrementing. • % is the remainder of the integer division. Relational operators: • <, >, <=, >=, ==, != Logical: &&=and, ||= or, !=not In addition of those operators there are several math routines in math.h sqrt, sin, cos, asin, acos etc.
How to solve a problem • Find the inputs and outputs of the problem. • Ask yourself if you have done something similar. • Identify the elements of the solution. • Take a numerical example and see the changes of the variables. • Write the code.
Inputs - Outputs Inputs are the elements / variables to start from. - Inputs must be read. - Input can be arguments within a function. Output(s) is represented by the problem result. - Outputs must be printed. - Outputs can be returned by a function.
The Process of Solving • Ask yourself if you have done something similar. • Solve the problem mathematically. • Identify the elements of the solution: • Break the problem into small blocks that you know how to. • Write functions / find snippets of code for each block. • Find the calculations / selections / repetitions • Write a pseudo-code in plain English.
Solving a triangle #include<stdio.h> #include<conio.h> #include<math.h> int main (int args,char ** argc){ double a, b, c, A, B, C, per, ar, r, R; printf("***************************\n\n"); printf("a=");scanf("%lf",&a); printf("b=");scanf("%lf",&b); printf("c=");scanf("%lf",&c); A=acos((b*b+c*c-a*a)/(2*b*c))*180/3.141592654; B=acos((a*a+c*c-b*b)/(2*a*c))*180/3.141592654; C=acos((a*a+b*b-c*c)/(2*a*b))*180/3.141592654 printf("\nThe angle 'A' is = %lf degres \n", A); printf("The angle 'B' is = %lf degres\n", B); printf("The angle 'C' is = %lf degres\n",C); printf(”\n\n****************************\n\n"); return1; }
C Statements. C statements give the flow of computation within C programs. • Simple statements: • expression; - to evaluate a C expression. • block {} - used to collect several statements in if, for, while. • Jump: • break - jumps outside of repetitions. • goto - jumps to a label. • return - gets outside of functions/routines • Selections • simple if - selects an alternative • complete if - selects from two alternatives • switch - selects from multiple alternatives.
C tests - if statement. If statement to select one choice if(test) { statement1; statement2; … } If statement to choose between two alternatives if(test) { statement1; statement2; … } else { statement 1; statement 2; … }
Minimum of two numbers. Example: Find the maximum/minimum value of a,b if(a<b) { max=b; min=a; } else { max=a; min=b; }
Max of 4 numbers. Given for integer numbers a, b, c, d then write a program to calculate the maximum value of them. Inputs: a, b, c, d – int Output: max – int. How to do it? read a, b, c, d; find max1 as the maximum of a and b find max 2 as the maximum of c and d find max as the maximum of max1 and max2 write mac
Max of 4 numbers. // find max between the two max-s if( max1>max2 ) { max=max1; } else { max=max2; } // print max printf("\n The maximun 'max'=%d \n",max); return1; } #include<stdio.h> #include<conio.h> int main (int args,char ** argc){ int a,b,c,d,max1,max2,max,min,min1,min2; //reading the variables printf("a=");scanf("%d",&a); printf("b=");scanf("%d",&b); printf("c=");scanf("%d",&c); printf("d=");scanf("%d",&d); // find max between a and b if( b>a ) { max1=b; } else { max1=a; } // find max between c and d if( d>c ) { max2=d; } else { max2=c; }
Test if three doubles form a triangle. #include<stdio.h> #include<conio.h> int main (int args,char ** argc){ double a,b,c,; int ans=1; printf("a=");scanf("%lf",&a); printf("b=");scanf("%lf",&b); printf("c=");scanf("%lf",&c); // test negative sides if( (a<=0) || (b<=0) || (c<=0)) { ans=0; } //test triangle inequality if( (a>=b+c) || (b>=c+a) || (c>=a+b)) { ans=0; } if(ans==1)printf("\n The numbers form a triangle"); else printf("\n The numbers do NOT form a triangle"); return1; }
To do List • Read more about if from the e-tutorial. • Solve the HW problems.
