Assoc. Prof. Dr. Tansu FİLİK

Transcription

1 Assoc. Prof. Dr. Tansu FİLİK

2 Bil 200 Week -2 Previously on Bil 200 Programming Languages (Machine Code, Assembly code, high-level languages) Compiler (translator) Software development (components of algorithm) Top-Down software development Elements of C-programming language

3 Bil200 Computer Programming Variables and Values Basic data types: Integer numbers Floating point type numbers Characters (letters) Character arrays (strings)

4 Bil200 Computer Programming Variables and Values int and float Integers (int) Floating point (real) numbers e-1-1e1

5 Variables and Values Characters (char) characters 'a' 'z' 'A' 'Z' '?' '0' '9 Special characters are obtained using a \ sign before the indicator. \n : skip to new line \t : tab skip 8 character spaces \' : print out ' \\ : print out backslash \ etc..

6 Exercises Exercise 1 Calculate the area of a triangle whose base length (b) and height (h) are given. Read b and h values Area ½ * b * h Print Area

7 Math Expressions They combine or change values of variables. Operators: + - * / % Functions: exp(), cos(), log() They return a value with a specific type.

8 Exercises Exercise 1 Calculate the area of a triangle whose base length (b) and height (h) are given. Read b and h values Area ½ * b * h Print Area

9 Exercises Exercise 2 For an initial amount of money M and a basic interest rate (F), calculate the amount of interest income at the end of a period of time. Read M and F interest M* F Total M + interest Print interest Print Total

10 Exercises Exercise 3 For an average speed H, calculate the required amount of time for a travel between two locations that have distance U. Read H and U time U/H Print time

11 Exercises Exercise 4 Write a list of commands to read midterm, homework, and final grades of a student and calculate the total grade. The weight of final is twice of the midterm. Midterm and home work have the same weight. Read midterm, homework, and final total midterm + homework + 2*final average total / 4 Print average

12 Unitary operations They are applied to single variables. Example i = +1; /* + used as unitary operator*/ j = -i; /* - used as unitary operator */ Single + indicates that the number is positive (obsolete). Single negates the variable or indicats a negative value.

13 Increment / decrement operators ++ is an increment operator. i++; means i = i + 1; -- is a decrement operator j--; means j = j - 1; According to using before or after the variable, the operators may work slightly differently. i++; or ++i; do the same thing, but inherently, they work in a different manner with a different set of machine code instructions.

14 Increment / decrement operators ++k increment k by 1, and return the result to the expression that uses ++k. k++ use the value of k in the expression that uses k++, and then increment the value of k by 1. --k decrement k by 1, and return the result to the expression that uses --k. k-- use the value of k in the expression that uses k--, and then decrement the value of k by 1.

15 Examples int k=0, m; m = ++k; int k=0, m; m = k++; int k=5, m, n=2; m = --k + n; int k=0, m, n=7; m = k n; m becomes 1 and k becomes 1 m becomes 0 and k becomes 1 m becomes 6 and k becomes 4 m becomes 6, k becomes 1, and n becomes 6

16 Examples d -= 4 (d = d - 4) e *= 5 (e = e * 5) f /= 3 (f = f / 3) g %= 9 (g = g % 9) If the value of i is 5; printf( "%d", ++i ); => Prints 6 on screen printf( "%d", i++ ); => Prints 5 on screen In both cases, the value of i after execution is 6.

17 Exercise Determine the values of the variables after the following lines. Do it by hand first, then try at the computer. int i, j, k; i = 2; j = 3 + i++; k = i; i *= ++k + j--; i /= k j;

18 Type casting Conversions between double and int

19 Type casting Supported integer types C language has several integer types. char 8 bit short 16 bit unsigned short 16 bit int 32 bit unsigned int 32 bit long int 32 bit unsigned long 32 bit

20 Type casting Supported floating types C language has several floating point types. float 32 bit double 64 bit long double 64 bit

21 Type casting Casting If both int and double (or float) is used in an expression, C compiler automatically does type casting. int k = 5, m = 4, n; double x = 2.5, y = 4.1, z; z = k + x; k variable is converted to double before the + operation. z = k / m; n = x * y; k/m is calculated, result is converted to double x*y is calculated as double, result is converted to int.

22 Type casting Casting The programmer can deliberately tell the compiler which type to use. int k = 5, m = 4, n; double x = 2.5, y = 4.1, z; z = (double) k + x; /* 7.5 */ z = (double) k / (double) m; /* 1.25 */ n = (int) x * (int) y; /* 8 */ y variable is casted to int

23 Type Casting Forced casting types do not change type of the variable, but the value is temporarily changed to the new type. int k=5; printf(".2f\n", (double) k); /* 5.00 */ printf("%d\n",k); /* 5 */ After these lines, k s type will still be int and its value is 5.

24 Operation precedence The order of executing an arithmetic expression is called operation precedence. C (and other languages) have some precedences of arithmetic operators. In order to evaluate the correct result of an expression, one must precisely know the operation precedence.

25 Operation precedence Use the PEDMAS rule to determine the precedences.

26 Operation precedence float float is a data type which gives more accurate numerical results, but requires more computation power and memory. Normally, computers perform integer operations faster. Example: float operation = * / 5 = 1 + (2 * 3) - (4.0 / 5) = = 6.2

27 Operation precedence Integers Expression may look deceiving. Be careful about performing integer operations. Example: (1 + 2) * (3-4) / 5 = ((1 + 2) * (3-4)) / 5 = (3 * -1) / 5 = -3 / 5 = 0

28 Operation precedence Floating points Example: The result is more accurate. ( ) * (3-4) / 5 = (( ) * (3-4)) / 5 = (3.0 * -1) / 5 = -3.0 / 5 = -0.6

29 Operation precedence Precedences : Extra info *, /, % have the same precedence. +, - have the same precedence. For the same precedence operators, the command is executed from left to right = (2 + 3) 1 = = (2 3) + 1 = 0

30 Assignment and operation precedences: a=0, b=1; x=(++a==b); x=2>=b; x=1 (true) x=1 (true)

31 Operator Precedence Operator Precedence! + - & highest * / % + - < <= >= > ==!= && = lowest

32 Comments / Documentation Documentation is an integral part of program development process. Documentation is aimed to explain how a program flows to those who try to read your program (which can be yourself). starts with /* and continues up to the next */ Comments within comments are not allowed.

33 Comments #include <stdio.h> /* Ekrandan girilen bir sayının karekökünü yazar. */ int main() { /* bir seyler yazalim /* hatali açıklama */ */ }

34 Coding style - indentation How to write intelligible codes

35 Coding style - indentation #include <stdio.h> int main() { int sayi; scanf("%d", &sayi); if( sayi < 10 ) { printf("az\n"); #include <stdio.h> int main(){ int sayi; scanf("%d",&sayi); if(sayi<10) { printf("az\n"); } return 0; } } return 0; }

36 Formatted writing printf ( ) ; This function is used for writing expressions on the screen in a formatted way. The usage is: printf ( format", var1, var2, ); format is a list of specifiers to indicate how to write the values of variables var1, var2, etc. Furthermore, you may write plain text there. float a ; int b ; scanf ( "%f %d", &a, &b ) ; printf ( "Şunları Girdiniz: %f ve %d \n", a, b ) ;

37 Formatted writing printf Format specifiers: d integer decimals l the variable is in long type e the float will be written in exponent form f a float will be written g prefers whether e or f style is more compact c writes a single character s writes a string (character array)

38 Formatted writing Format specifiers Symbol Meaning %i, %d Integer (int) %c Character (char) %s String %f, %e float %g Float - double %ld Long integer %o Octal (8) %x Hexadecimal (16)

39 Formatted output 12 ay içinde yapılan borç miktarını bulunuz ay=12; => int harcama=111.1; => float gelir=100.0; => float

40 Formatted output