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Introduction to programming

Introduction to programming. C++. Constants vs. Variables. Constants Numeric – a numeric value Ex. 5, -7, 98.6 Character – a single symbol Ex. ‘A’, ‘a’, ‘?’, ‘ ‘, ‘5’ String – a group of one or more characters Ex. “Hello”, “98.6”, “Mary had a little lamb.”

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Introduction to programming

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  1. CISP 1010 - Computer Science I Introduction to programming C++

  2. CISP 1010 - Computer Science I Constants vs. Variables • Constants • Numeric – a numeric value • Ex. 5, -7, 98.6 • Character – a single symbol • Ex. ‘A’, ‘a’, ‘?’, ‘ ‘, ‘5’ • String – a group of one or more characters • Ex. “Hello”, “98.6”, “Mary had a little lamb.” • Note: Usually referred to as a literal • Variables • Symbolic name for a memory location • Contents may change • May be of any supported data type • Ex: x, val, Age, userName

  3. CISP 1010 - Computer Science I Primitive Data Types in C++ • Integer values • int– used for most integer values • short (aka short int) – used to hold “small” values • long (aka long int) – used when larger capacity is needed • may be positive or negative unless specified as unsigned • Floating point values • float– have a whole number and a fractional part • double – used when a higher degree of precision is needed • may be positive or negative unless specified as unsigned • Character values • char – hold a single letter, digit or symbol • Boolean values • bool – holds a true or false value

  4. CISP 1010 - Computer Science I Variable Names in C++ • Generally can be any combination of alphabetic characters or digits or and underscore except: • Whitespace – no space, tab, return, etc. • Use capitalization or underscore to imply a space • myArray or first_number • No digits or special characters in first position • No operators such as + or – • May begin with underscore : _val • Names are case sensitive • Ex: age, Age, age1, userName, UserName are all unique • Can not be a C++ reserved word • Ex: int, float, cin, cout, sizeof all mean something to C++

  5. CISP 1010 - Computer Science I Assignment Operator • To assign a value to a variable the = operator is used • age = 25; • number = 0; • temp = 98.6; • Note: each statement ends in a semi-colon • Assignments may use constants, variable or expressions • number = 7; // number now holds 7 rather than 0 • number = age; // number now holds 25 rather than 7 • number = number + 1; // number now holds 8

  6. CISP 1010 - Computer Science I Creating Variables • Variables have to be declared (to the compiler) • intval; • float celsius; • double standard_deviation; • bool flag; • Multiple variables of the same type can be declared • int x, y, z; • char a, b, ch; • Variables can be initialized • float temp = 98.6; • char letter = ‘a’; • bool state = true; • intnum, val = 3; // note that only val is initialized to 3 here

  7. CISP 1010 - Computer Science I Binary Arithmetic Operators • + used to add two values • x = y + 1; // x holds sum of y plus 1, y is unchanged • -used to subtract a value from another values • x = y – 1; // x holds difference, may be negative • * used to multiply a value times another • z = x * y; // z holds product, x & y unchanged • / used to divide a value by another • quotient = x / y; // hopefully quotient can hold a float • % used to extract the remainder after long division • z = x % 2; // z holds the remainder and will be an integer • performed modular arithmetic

  8. CISP 1010 - Computer Science I Expressions • Expressions may include variables and constants • x + 1 • p * q • An assignment statement can have an expression on the right side only • y = x + 1; • z = x * y; • q = q * q; • p * q; // a complete statement with no assignment • Traditional algebra statements must be rewritten • a + b = c; // invalid • c = a + b; // valid • Multiple assignments are valid as long as they can be evaluated • a = b = c; or a = b = 1; or a = b = c + 1; but not a = b + 1 = c + 1;

  9. CISP 1010 - Computer Science I Operator of Precedence • When multiple operators are used in the same expression there is a precedence that determines the order they are evaluted. • High order: *, /, % • Lower order: +, - • Operators of equal order are evaluated left to right • Assume: • intval, a = 3, b = 2, c= 5; • val = a + b * c; // mutiplication 1st so val is now 13 • val = a + b – c; // addition 1st so val is now 0 • val = a + 3 * b + 1; // val is now 10 • Highest order: ( ) can override precedence • val = ( a + 3 ) * ( b + 1 ); // val is now 18

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