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Munster Programming Training

Munster Programming Training. What is C? . C is a programming language. It communicates to the computers what to do. It solves various problems from scientific to entertaining. Why C? It is simple, fast, procedural etc. It has several extensions C++, C# … It is the language of Sciences.

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Munster Programming Training

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  1. Munster Programming Training

  2. What is C? C is a programming language. • It communicates to the computers what to do. • It solves various problems from scientific to entertaining. Why C? • It is simple, fast, procedural etc. • It has several extensions C++, C# … • It is the language of Sciences. A C program is a sequence of C routines which must include main.

  3. The words of C? C programs communicate to the computer using “words”. C Key words are names for: • Data types: void, int, long, double, float • Statements: if, while, for, Programmers words / user words. • Names for variable, routines. Rules: • User names use letters, digits, _. • C is case sensitive Example: a, b, c, A, B1,C_1, max_two_numbers

  4. What is a C program like? # include <stdio.h> # include <math.h> int main(int args, char ** argc) { printf("Hello from C \n"); return 1; } Sections of C programs: • Include declarations • The header of main. • The block of main. • Declare all the variables. • Read all the inputs. • Generate the output. • return 1; # include <stdio.h> # include <math.h> int main(int args, char ** argc) { // nothing in the program return 1; }

  5. More on these examples • Include declarations for the libraries we use. • stdio.h  for input/output. • math.h  for maths functions. • stdlib.h for standard c functions. • In the main function • // are comments • printf(); is a C function to print/display/write etc. • scanf (); is a C function to read an input value. • A sequence of characters between ” ” is a string.

  6. Another program. # include <stdio.h> # include <math.h> int main(int args, char ** argc) { int a, b; double mean; printf("a="); scanf("%d", &a); printf("b="); scanf("%d", &b); mean=(a+b)/2.; printf("mean=%lf \n\n", mean); return 1; } Three variables a, b, mean. • They are declared. • The inputs a, b are read. • The output mean is calculated and written. Each command ends with “;”. Writing style: • indent your lines • write several statement on the same line • align brackets • Finish each line with ; Same rules as in Maths: +, -, /, *, () etc

  7. Read and Write printf(“format”, var) for writing scanf(“format”,&var) for reading printf(“text %spec \n”, var1); printf(“text %s1 text %s2 text …\n”, var1,var2,…); - format specificators: %d, %ld, %f, %lf. - \n special character for newline. scanf(“%spec”,&var); No text is allowed in the format. printf("a="); scanf("%d", &a); printf(“a=%d”,a);

  8. Read and Write - Examples Read an int variable a. printf(“a=”); scanf(“%d”,&a); Write an int variable a. printf(“a = %d \n”, a); Read two variables x and y. printf(“Type the Values for x and y”); scanf(“%d %d”,&x, &y); Write two int variables x,y. printf(“a = %d b= %d \n”, x, y);

  9. C Data Types. In Mathematics there are several sets of numbers: N, Z, Q, R. In C there are several data types (sets of C numbers): • Integers: char, short, int, long. • Reals: float and double. int -2^15, 2^15-1 unsigned int 0, 2^16 long -2^31, 2^31-1 unsigned short 0, 2^32 float 6 exact decimals double 10 exact decimals C literals: integer numbers: sequence_of_digits. real numbers: sequence_of_digits.sequence_of_digits characters: ‘ch’ string: “sequence_of_characters”

  10. C Declaration. In a C program ALL VARIABLES MUST BE DECLARED once. Types of declarations: • type var; • type var=value; • type var1,var2,..; Example: • int a,b,c; • double x,y=0.; • double x, a; Declarations go in the first part of a block. ALL VARIABLES MUST BE READ/INITIALISED.

  11. C Arithmetic C variables form expressions using operators: Arithmetic operators: • +, -, *, / • ++, -- for incrementing and decrementing. • % is the remainder of the integer division. Relational operators: • <, >, <=, >= • ==, != Logical: &&=and, ||= or, !=not Assignment: = In addition of those operators there are several math routines in math.h sqrt, sin, cos, asin, acos etc.

  12. Examples int a,b,c; double x,y; a=1;b=2;c=4; a=b+c; // a=6 b=c+2; // b=6 a=a+1; // a increases with 1 ==> a++; x=PI;y=sin(x); x=asin(y/2); a=b=2; // initialise a and b with 2. a==b; // compare a and b.

  13. C tests - if statement. if(test) { statement1; } else { statement 2; } or chooses one alternative if(test) { statement1; } If statement chooses between two alternatives if(test) statement1; else statement 2; or chooses one alternative if(test)statement1; On the branches we have only one statement. If more use a block {} Example: Maximum value of 2 numbers if(a<b) { max=b; } else { max=a; }

  14. Max of two numbers # include <stdio.h> # include <math.h> # include <conio.h> int main(int args, char ** argc) { int a, b, max; printf("a="); scanf("%d", &a); printf("b="); scanf("%d", &b); if(a<b) { max=b; } else { max=a; } printf(”max=%d \n\n", max); return 1; }

  15. To do List • Read more about C types, declarations, operators from the e-tutorial. • Solve the HW problems • Visit the page of AISPC.

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