C/C++ Operators

1. C/C++ Operators Binary Operators: Operators Between Two Operands: Operator Meaning Example Definition. + Addition x = 6 + 2; Add the values on either side of + - Subtraction x = 6 - 2; Subtract right value from left value Multiplication x = 6 * 2; Subtract right hand side values * / Division x = 6/2; Divide left value by right value % Modulus x = 6 % 2; Remainder of left divided by right What about exponentiation??? Either x = 6 ^ 2 OR x = 6 ** 2 ??? No Such Thing: You must write your own function (Or use an available one) Dividing 2 real numbers yields EXACT results NOTE: Dividing 2 Integers yields TRUNCATED results Why??

2. C/C++ Operators • Previously, we talked about how integers were stored. • For example, we said the declaration shorts1 = 56, s2 = 17; Asks for two 16-bit integer locations (s1 and s2) and stores the values 56 and 17 in them (respectively) Var/Locs1: 5610 Var/Locs2: 1710 We know that if we divide 56/17 (on a calculator) you would get the value 3.2941176470588235294117647058824 But, how do you store a mantissa as an integer?? (You don’t) 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1 1 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 1 OK – But what if I wanted to get the real answer above?? All Integers can be rewritten (as floats (casting)) The opposite is NOT true Decimal to Binary Converter

3. C/C++ Operators Consider (i.e., enter, build and run) the code below: #include"stdafx.h" #include<iostream> usingnamespacestd; voidmain() { ints1 = 56, s2 = 17; cout << s1 << " divided by " << s2 << " is " << s1/s2 << endl; cout << "Casting " << s1 << " and " << s2 << " and then dividing yields: " << (float)s1/(float)s2 << endl; } The output should appear as:

4. C/C++ Operators There is one additional binary Operator we need to discuss in more detail: The Modulus operator Add the following line to your program, compile and run: cout << "The remainder of 9/2 is " << 9 % 2 << endl; How is this useful?? There are a number of uses. We are going to take a look at one example: Converting decimal values to binary

5. C/C++ Operators There is one additional binary Operator we need to discuss in more detail: The Modulus operator Add the following line to your program, compile and run: cout << "The remainder of 9/2 is " << 9 % 2 << endl; How is this useful?? There are a number of uses. We are going to take a look at one example: Converting decimal values to binary

6. Converting from decimal to binary Dividing any integer by 2 means that the remainder must be either 0 or 1 A few slides ago, we noted that = 1110002 5610 How can we verify this?? When you first learned division, you probably were taught to do it as follows: 28 14 7 1 0 3 2 goes into 3, 1 times. 1 times 3 is 3. Subtracting -3 from 7 leaves a remainder of 1 2 goes into 7, 3 times. 2 times 3 is 6. Subtracting -6 from 7 leaves a remainder of 1 2 goes into 14, 7 times. 2 times 7 is 14. Subtracting -14 from 14 leaves a remainder of 0 2 goes into 28, 14 times. 2 times 14 is 28. Subtracting -28 from 28 leaves a remainder of 0 2 goes into 56, 28 times. 2 times 28 is 56. Subtracting -56 from 56 leaves a remainder of 0 2 goes into 1, 0 times. 0 times 1 is 0. Subtracting 0 from 1 leaves a remainder of 1 2 2 2 2 2 2 1 56 3 28 7 14 -28 -6 -0 -2 -56 -14 0 1 0 0 1 1

7. Converting from decimal to binary Let’s rewrite this procedure in a simpler form Pass Gathering the remainders from last to first: 2 0 remainder quotient 1 1 1 0 0 0 = 56 0 2 28 How do we do that?? 56 0 1 7 3 1 14 2 2 2 2 0 2 We’re going to have to go over your first abstract data type: An Array 1 3 1 4 1 5 0 Stop when the quotient becomes 0

8. Arrays An array is an arrangement of similar basic data types Let’s create an array of short integers short binary[15], temp[15], decval = 56, reverse = 0, index = 0, i; Next, we’ll create the array as we did before while (decval > 0) { temp[index] = decval % 2; index++; decval = decval/2; } index--; Now we need to reverse the order of the array i = index; while (reverse <= index) { binary[reverse] = temp[i]; reverse++; i--; } The complete programming (including the printing of the result) is given on the next slide

9. Arrays #include"stdafx.h" void main() { shortbinary[15], temp[15], decval = 177, reverse = 0, index = 0, i; while (decval > 0) { temp[index] = decval % 2; index++; decval= decval/2; } index--; for (i = 0; i <= index; i++) printf("%d",temp[i]); printf("\n\n"); i = index; while (reverse <= index) { binary[reverse] = temp[i]; printf("%d %d %d\n",i, reverse, binary[reverse]); reverse++; } i--; for (i = 0; i <= index; i++) printf("%d", binary[i]); printf("\n"); } As usual, you should enter the code, compile it, and run it

10. = x = 3 Assignment Operators: Assigning Values to RAM: Operator Example Definition. = x = 6 + 2; Location x will get the value 6 + 2 ( = 8) += x += 3 Same as x = x + 3: IF x contained the value 4, it now contains the value 7 Same as x = x - 3: IF x contained the value 4, it now contains the value 1 *= x *= 3 Same as x = x * 3: IF x contained the value 4, it now contains the value 12 /= x /= 3 Same as x = x / 3: IF x contained the value 4: IF x is a float (real), it now contains 1.33 IF x is an integer, it now contains the value 1 %= x %= 3 Same as x = x % 3: IF x contained the value 4, it now contains the value 1 (3 goes into 4 Once with ONE left over)

11. Unary Operators: Operators on a single Operand: Operator Meaning Example Definition. - Minus Sign x = -2; Assign a negative value + Plus Sign x = +2; Assign a Positive value ++ Increment x = ++y; Prefix Notation OR x = y++; Postfix Notation -- Decrement x = --y; Prefix Notation OR x = y--; Postfix Notation Prefix and Postfix Notation?? What’s that all About ??? Consider the following section of c code: int x,y,a,b; a = b = 1; // Initialize the variables (locations) with the value 1 x = 2 * ++a; // PREFIX Notation: First increment a by 1 (a = 2) // Then Multiply by 2 & assign to x (x=2*2) y = 2 * b++; // POSTFIX Notation: First multiply b by 2 & assign to y (y=1*2) // Then increment b by 1 (b = 2) printf("%d %d\n",x,y); // The Output would appear as:4 2

12. There are two (2) Additional Unary Operators: sizeof Return the size of the operand (in bytes) Consider the following section of c code: int i = 12; float f = -123.45; printf("%d sizeof = %d\n",i,sizeof i); // would produce: 12 sizeof = 2 printf("%7.2fsizeof = %d\n",f,sizeof f); // would produce: -123.45 sizeof = 4 (type) Convert a value to the specified data type Consider the following section of c code: int a = 4; float b = 12.245; printf("%d %ld\n",a,(long) a); // would produce: 44 printf("%d %f\n",a,(float) a); // would produce: 4 4.000000 printf("%f %d\n",b,(int) b); } // would produce: 12.24500012

13. Relational Operators: Operators on two Operands Yielding a T/F Answer: Operator Meaning Example Definition. < x < 2; False if x contains the value 2 Less Than x <= 2; True if x contains the value 2 <= Less Than OR Equal To = = x = = 2; True if x contains the value 2 Equal To ! = x ! = 2; False if x contains the value 2 Not Equal To > x > 2; False if x contains the value 2 Greater than >= x >= 2; True if x contains the value 2 Greater than OR Equal To False if x contains the value 2 x > 2 && x < 4 && And | | True if x contains the value 2 x = = 2 | | x = = 4 Or ! False if x contains the value 2 Not ! (x = = 2)

14. Order of Operations: Order Operator 1 ( ) 2 + - ++ -- (unary) ! (Rel) 3 * / % 4 + - (binary) 5 < > <= >= 6 == != && 7 8 | | = 9 Given:int a = 1, b = 2, c = 3, d = 4, e = 5, f = 6, g = 7, h = 8; What is the value of the statement: a = (a * ((b + c) % d) / e) - (f * g + 6) * h / 4 + 1;

15. Given:int a = 1, b = 2, c = 3, d = 4, e = 5, f = 6, g = 7, h = 8; - 96 + 1 = - 95 0 - 96 = - 96 384 / 4 = 96 1 / 5 = 0 48 * 8 = 384 1 * 1 = 1 5 % 4 = 1 42 + 6 = 48 2 + 3 = 5 6 * 7 = 42 a = (a * ((b + c) % d) / e) - (f * g + 6) * h / 4 + 1;

16. Example 2: Given:int a = 1, b = 2, c = 3, d = 4, e = 5, f = 6, g = 7, h = 8; Evaluate: ++a * b-- + c % d / e - f-- * g + 6 * h++ / b + h; 2 2 * 2 = 4 3 % 4 = 3 3 / 5 = 0 6 * 7 = 42 6 * 8 = 48 48 / 2 = 24 4 + 0 = 4 4 - 42 = - 38 - 38 + 24 = - 14 - 14 + 8 = - 6 Note that now: a = 2, b = 1, f = 5, h = 9

17. Example 3: Given: int a = 1, b = 2, c = 3, d = 4; Consider the statement: a > b || b < c && c == 3 || d < 4 && b != c False True False True True False True True True

18. Conversion specifiers for scanf and printf: Specifier(s) Output Example %c Single Character B %d %i Signed decimal Integer 457 %u Unsigned decimal Integer 7832 %ld %lu Signed/Unsigned long Integer -345 64 %f Signed floating-point, decimal notation -6.576 -4.5e3 2.1E-2 %e %E Signed floating-point, e or E notation -2.1 4.56E4 %g %G Use shorter or %f or %e (%f or %E) Long double floating-pt (also %LE) 7.32 -6.1e4 %Lf %Le %o Unsigned octal notation 4271 %x %X Unsigned hexadecimal notation 4d2a F6B %s Character string Hello %p Pointer (address) 4FF0: 8BC1 %% Print a % sign % Additional information about printf/scanfspecifiers can be found in the Supplementary Materials Link

21. Additional Precompiler Directives User Defined constants: #define PI = 3.15149 User Defined constants: #define SQUARE (x) x * x // macro example.cpp : Defines the entry point for the console application. #include "stdafxh" #include <iostream> using namespace std; #define PI 3.15149 #define SQUARE(X) X*X void main() { float area, r = SQUARE(3.5); area = PI * r; cout << "The area is:" << area << endl; }