Basic data types Derived (composite) data types int arrays (including C strings) char structs float classes (C++) bool pointers string Data in a program can be constant (literal) or variable. constant variable 5 int i; 5.0 float f; '5' char c; "5" string s;
int a, b; // "little boxes" can store one int value int num; // some part of memory of certain sizeSize of int variable varies by machine: Size determines range of integer values.
old Turbo compilers: usually 2 bytes -32768 thru +32767 Now: 4 bytes ~-2 billion thru ~+2 billionValues outside the range don't exist in the computer.
Even with 4 byte int, this overflow problem exists.
int a, b; a = 2000000000; b = 1000000000; cout << a+b; // outputs -1294967296, ie. garbage but no error indication.overflow.cpp Try it
Variations on int (useful for larger ranges)
short: maybe smaller than int, e.g. 2 bytes. (save memory) long: on PC's is 4 bytes, so the 4 billion range, i.e. same as int. unsigned: positives unsigned long int range: 0 thru ~4 billion long long: 64-bit intRun the sizes.cpp to see what the sizes of numeric types are.
double 8 bytes; ~14 digits of accuracy; bigger range too. All real number constants in program are double.
All the number types can be freely mixed in expressions. The only questionable thing is to assign a float or double value to an int variable because it will be truncated (everything to the right of the decimal point is chopped off).
int i; float f; double d; f = i * i; //OK f = i * f; //OK i = f + 1; //i is int, only will store integer part of expression. Avoid
/ is division operator. If both values are integers,
will do integer division (whole number division) 7 / 2 == 3
One or both operands have to be real number for real division: 7.0 / 2 == 3.5
If have two ints and want to divide and get real result need to cast (convert) one or both to float:
int a, b; a = 7; b = 2; cout << a / b << endl; // 3 is output cout << float(a) / b << endl; // 3.5 is output //value of a changed to float (a itself is still an int variable and its value is still int 7)
#include <iomanip> //at top with other includes. to use the "set" manipulators. //field width. use that many positions for value (int, float, string) cout << setw(5) << a << setw(4) << b << endl; //endl manipulator Adds a newline and flushes output stream. // real values: cout << setprecision(2); // no more than 2 digits after decimal point // applies to all floats in rest of program (or until another setprecision) //to always output the . and the precision: do this "magic incantation" cout << setiosflags(ios::fixed|ios::showpoint); //OR cout << fixed << showpoint; // floats will be output xxx.yy wxyz.dd Useful for $$$.centsNext (char)