Structure of a C Program

Transcription

1 ummer School Computer Sc & Engg: IIT Kharagpur 1 Structure of a C Program

2 ummer School Computer Sc & Engg: IIT Kharagpur 2 #include <stdio.h> // cpp directive int hcf(int, int); // Function Interface int main() { // main function int large, small; printf("enter two non-ve integers\n"); scanf("%d%d", &large, &small); printf("hcf(%d, %d) = %d\n", large,small,hcf(large,small)); return 0; } // main ends sample.c

3 ummer School Computer Sc & Engg: IIT Kharagpur 3 int hcf(int sml, int lrg){ // Function int rem; // definition while(sml!= 0){ rem = lrg%sml; lrg = sml; sml = rem; } return lrg; } // Definition ends

4 ummer School Computer Sc & Engg: IIT Kharagpur 4 Structure of an OCAML Program (* sample.ml: An OCAML program *) exception BothZero (* Exception *) exception DataNegative (* Exception *) let rec hcf sml lrg = (* Another function *) if sml = 0 then lrg else (hcf (lrg mod sml) sml);; let main() = (* Function definition *) print_string("enter two non-negative integers\ let m = read_int() and n = read_int() in

5 ummer School Computer Sc & Engg: IIT Kharagpur 5 if m<0 n<0 then raise DataNegative; if m=0 && n=0 then raise BothZero else Printf.printf "hcf(%d, %d) = %d\n" m n (hcf m n);;

6 ummer School Computer Sc & Engg: IIT Kharagpur 6 File Name File name of a C program ends with.c and the file name of an OCAML program ends with.ml in the previous examples they are sample.c and sample.ml.

7 ummer School Computer Sc & Engg: IIT Kharagpur 7 Structure of a C Program It is a collection of preprocessor directives, functions and declarations. A function named main() is mandatory.

8 ummer School Computer Sc & Engg: IIT Kharagpur 8 A Preprocessor Directive #include <stdio.h> A line starting with a sharp sign # is a C preprocessor directive.

9 ummer School Computer Sc & Engg: IIT Kharagpur 9 Function Interface or Prototype int hcf(int, int); The prototype directs the compiler to generate correct invocation code. The function hcf() is used (called/invoked) in the function main() before it is defined.

10 ummer School Computer Sc & Engg: IIT Kharagpur 10 A Function Definition int hcf(int sml, int lrg){ // Function int rem; // definition while(sml!= 0){ rem = lrg%sml; lrg = sml; sml = rem; } return lrg; } // Definition ends A definition specifies the name, parameters, computation and the type of the return value.

11 ummer School Computer Sc & Engg: IIT Kharagpur 11 Parameters and Return Value int hcf(int sml, int lrg) The function hcf takes two parameters, both are of type int and also gives back (returns) a value of type int after the computation a. a Mathematically hcf: int int int.

12 ummer School Computer Sc & Engg: IIT Kharagpur 12 Function main() int main() is also a function and its presence in a C program is mandatory. In this program main() does not take any parameter.

13 ummer School Computer Sc & Engg: IIT Kharagpur 13 Variable Declaration int large, small; large and small are called local variables to the function main(). Similarly rem is a local variable to the function hcf().

14 ummer School Computer Sc & Engg: IIT Kharagpur 14 Statements rem = lrg%sml; lrg = sml; while( ){ } return lrg;

15 ummer School Computer Sc & Engg: IIT Kharagpur 15 Operators Assignment: = Relational:! = Mod: %

16 ummer School Computer Sc & Engg: IIT Kharagpur 16 Library Functions Reads from Keyboard: scanf() Writes on the VDU: printf() Library functions are supplied along with the compiler.

17 ummer School Computer Sc & Engg: IIT Kharagpur 17 Compile and Run $ cc -Wall sample.c $./a.out Enter two non-ve integers HCF(12, 18) = 6

18 ummer School Computer Sc & Engg: IIT Kharagpur 18 Structure of an OCAML Program It is a collection of function definitions and function invocations.

19 ummer School Computer Sc & Engg: IIT Kharagpur 19 Definition of hcf let rec hcf sml lrg = (* function hcf *) if sml = 0 then lrg else (hcf (lrg mod sml) sml);; A definition specifies Name: hcf (global), Parameters: sml lrg (local), computation such as expressions etc.

20 ummer School Computer Sc & Engg: IIT Kharagpur 20 Note The interpreter infers the types of different objects. The type inferencing takes place at the time of compilation. It is known as static type inferencing.

21 ummer School Computer Sc & Engg: IIT Kharagpur 21 Function main() main() is another function (no special status). It is of type unit -> unit, that means it does not take any parameter or returns any value. This may be compared with type void of C.

22 ummer School Computer Sc & Engg: IIT Kharagpur 22 Parameters and Return Value In the function hcf, the parameters are sml and lrg. Both are of type int. This inference is drawn from the comparison of sml with integer 0, and the arithmetic operator mod between fst and sml.

23 ummer School Computer Sc & Engg: IIT Kharagpur 23 Expressions lrg mod sml sml = 0 if sml = 0 then lrg else...

24 ummer School Computer Sc & Engg: IIT Kharagpur 24 Local Binding of Names let m = read int() and n = read int() in m, n are local names (they are not variables like C), they bound to the data of type int read from the keyboard. They are visible only to the remaining portion of the code of main.

25 ummer School Computer Sc & Engg: IIT Kharagpur 25 Library Functions print string() read int() Printf.printf Library functions are supplied along with the interpreter. [read_int() takes one input per line.]

26 ummer School Computer Sc & Engg: IIT Kharagpur 26 CPP Compiler Assembler Linker (sample.c) C Program Object Module/ Library Linker C Preprocessor Modified C Program C Compiler Assembler Assembly Language Program (sample.s) Executable Module (a.out) Object Module (sample.o)

27 ummer School Computer Sc & Engg: IIT Kharagpur 27 Laboratory Session

28 ummer School Computer Sc & Engg: IIT Kharagpur 28 Activity - VIII It is known that the sum of internal angles of a triangle is 180 (π c ), that of a quadrilateral is 360 (2π c ), and for a pentagon it is 540 (3π c ). In general the sum of the internal angles of an n-sided polygon is 180(n 2) degrees (n 2)π c. Write a C program that reads the number of sides of a polygon (n) and prints the value of the sum of internal angles.

29 ummer School Computer Sc & Engg: IIT Kharagpur 29 Activity - VIIIa Write a OCAML function for the previous problem.

30 ummer School Computer Sc & Engg: IIT Kharagpur 30 Quiz on C Program Write answers in your note-book. 1. What is the type of the variable corresponding to the sides of a polygon? 2. Name three operators you used. 3. What is the format string for reading the variable for the number of sides, n?

31 ummer School Computer Sc & Engg: IIT Kharagpur 31 Quiz on OCAML Function Write answers in your note-book. 1. How many operators are there? 2. How many parameters are there? 3. How do you modify the function to get a more meaningful output? 4. How do you modify the program that reads the number of sides of the polygon?

32 ummer School Computer Sc & Engg: IIT Kharagpur 32 Activity - IX Write a C program that reads the constant velocity v (m/sec) of an object and the time t (sec) of its travel. It prints the distance d (m) traversed by the object in t sec. [d = vt]

33 ummer School Computer Sc & Engg: IIT Kharagpur 33 Quiz on C Program Write answers in your note-book. 1. What are the types of the variables corresponding to velocity, time and distance? 2. Name two operators you used. 3. What is the format string for reading the variables.

34 ummer School Computer Sc & Engg: IIT Kharagpur 34 Activity - IXa Write an OCAML that takes the constant velocity v (m/sec) of an object and the time t (sec) of its travel as parameters. It returns the distance d (m) traversed by the object in t sec. [d = vt]

35 ummer School Computer Sc & Engg: IIT Kharagpur 35 Quiz on OCAML Function Write answers in your note-book. 1. What are the operators you have chosen? 2. Modify it to a program that reads the velocity and time from the keyboard and prints the output properly.

36 ummer School Computer Sc & Engg: IIT Kharagpur 36 Activity - X Modify your program that takes v and d as inputs and prints the time taken to travel.

37 ummer School Computer Sc & Engg: IIT Kharagpur 37 Activity - XI Consider the following polynomial p(x) = 2.5x x 2 + 4x + 9 where x is a variable (unknown) a. Write a C program that reads a value of x and evaluates the value of the polynomial for the input value of x. It prints both the value of x and the value of p(x). a It is a cubic polynomial of x.

38 ummer School Computer Sc & Engg: IIT Kharagpur 38 Note Let the input value of x be 2.0. The program computes p(2.0) = = 59.0 The program prints p(2.0) = Note that x 3 x*x*x.

39 ummer School Computer Sc & Engg: IIT Kharagpur 39 Activity - XIa Write an OCAML function to compute the polynomial. It read the value of the input from the keyboard.

40 ummer School Computer Sc & Engg: IIT Kharagpur 40 Quiz Write answers in your note-book. 1. How many multiplications are you performing? Can you reduce their number? In a computer multiplication and division often takes more time than addition and subtraction. 2. What is your print format?

41 ummer School Computer Sc & Engg: IIT Kharagpur 41 Activity - XII Write a C program that reads a number with a decimal point, (floating point number) of the form nnnn.fffff e.g It stores the integral part nnnnn (237 in the example) in a variable of type int and the fractional part,.ffffff (.512), in a variable of type float or double. Finally it prints both the parts separately.

42 ummer School Computer Sc & Engg: IIT Kharagpur 42 Activity - XIIa Following OCAML function does the job: let intfrac x = (int_of_float) x, x -. (float) (int_of_float x));; Write a CAMAL program using the function that reads the data from the keyboard and prints it on the VDU.

43 ummer School Computer Sc & Engg: IIT Kharagpur 43 Activity - XIII Write a C program that takes an input of the form a.b, where both a and b have one or two digits e.g. 1.2, 12.5, 0.19, 2.0, etc. The program prints the number in n p q form e.g /10, /10, 19/100 etc.

44 ummer School Computer Sc & Engg: IIT Kharagpur 44 Activity - XIIIa Write an OCAML program to solve the previous problem.

45 ummer School Computer Sc & Engg: IIT Kharagpur 45 Activity - XIV Write a C program that reads the lengths of the three sides of a triangle a, b and c and uses the Heron s formula to calculate the area of the triangle. The area A = s(s a)(s b)(s c), where s is the semiperimeter of the triangle, s = a+b+c 2.

46 ummer School Computer Sc & Engg: IIT Kharagpur 46 Note You have to include math.h #include <math.h> and link the mathematical function library. $ cc -Wall -lm file.c

47 ummer School Computer Sc & Engg: IIT Kharagpur 47 Activity - XIVa Solve the same problem in OCAML.

48 ummer School Computer Sc & Engg: IIT Kharagpur 48 Activity - XV Write a C program that takes an input of the form a.b, where both a and b have one or two digits e.g. 1.2, 12.5, 0.19, 2.0, etc. The program prints the floating point number of the form b.a e.g. 2.1, 5.12, 19.0, 0.2, etc.

49 ummer School Computer Sc & Engg: IIT Kharagpur 49 Another Version of OCAML HCF Program (* samplea.ml: An OCAML program *) let hcf sml lrg = let l = ref lrg and s = ref sml in while!s <> 0 do let rem = ref (!l mod!s) in l :=!s; s :=!rem done; print_int(!l);;

50 ummer School Computer Sc & Engg: IIT Kharagpur 50 let main() = (* function main *) print_string("enter two non-negative integers\ let m = read_int() and n = read_int() in Printf.printf "hcf(%d, %d) = " m n; hcf m n ; print_newline();; main();;

51 ummer School Computer Sc & Engg: IIT Kharagpur 51 OCAML Program VIIIa (* Assignment VIIIa: Internal angles of a polygon *) let intang = function n -> Printf.printf "Sum of the internal angles of a %d-gone is %d deg\n" n (180*(n-2));;

52 ummer School Computer Sc & Engg: IIT Kharagpur 52 OCAML Program IXa (* Assignment IXa: distance covered with linear velocity *) let dist() = print_string("enter the velocity (m/sec): "); let v = read_float() in print_string("\nenter the time (sec): "); let t = read_float() in print_string("the distance covered with velocity ") Printf.printf "%6.2f m/sec in time %6.2f sec is %6.2f m\n" v t (v *. t) ;;

53 ummer School Computer Sc & Engg: IIT Kharagpur 53 OCAML Program XIa (* Assignment XIa: Evaluating a polynomial *) let polyval() = print_string("enter the value of x: "); let x = read_float() in Printf.printf "The value of the polynomial for x = %f is %f\n" x (x*.(x*.(2.5*.x+.5.5)+.4.)+.9.);;

54 ummer School Computer Sc & Engg: IIT Kharagpur 54 OCAML Program XIIa (* Assignment XIIa: int and frac *) let intfrac() = print_string("enter the value of x: "); let x = read_float() in let n = int_of_float x in Printf.printf "%f = (%d, %f)\n" x n (x -. (float) n);;

55 ummer School Computer Sc & Engg: IIT Kharagpur 55 OCAML Program XIIIa (* ass13a.ml: Int and frac *) let floattorat() = let s = read_line() in let n = int_of_float (float_of_string s) in let t = String.copy s in (* t = s does not work *) s.[0] <- 0 ; s.[1] <- 0 ; if n > 9 then s.[2] <- 0 ; let f = int_of_string s in Printf.printf "%s = %d + %d" t n f; if f < 10 then print_string("/10\n")

56 ummer School Computer Sc & Engg: IIT Kharagpur 56 else print_string("/100\n");;

57 ummer School Computer Sc & Engg: IIT Kharagpur 57 OCAML Program XIVa (* ass14a.ml: Area of a Triangle *) let triarea() = print_string("enter three sides of a triangle: "); let a = read_float() and b = read_float() and c = read_float() in let s = (a+.b+.c)/.2.0 in let area=sqrt (s*.(s-.a)*.(s-.b)*.(s-.c)) in Printf.printf "Sides: %6.2f, %6.2f, %6.2f Area: %6.2f\n" a b c area;;