7/20/2020 Beginning C Programming For Dummies Cheat Sheet
Beginning C Programming For
Dummies Cheat Sheet
From Beginning Programming with C For Dummies
By Dan Gookin
The best way to learn programming is to start with a fundamental language like C.
Nearly every other popular language today borrows from C. Whether you’re
curious about programming, need to pass a college course, or want to start your
own app business, learning C is the right place to begin.
Understanding the C Language Skeleton
Most coding starts with a C language structure. This skeleton includes the basic
bones upon which most programs are written. Use this simple skeleton to get
started:
#include <stdio.h>
int main()
{
return(0);
}
Traditionally, the program begins with preprocessor directives plus prototypes.
The #include statements bring in header files, such as stdio.h, the standard
input/output header file.
The primary function in all C code is main(), which is the first function that’s run
when the program starts. The main() function is an int function, so it must return
an integer value. All the function’s statements are enclosed in curly brackets, or
braces.
C Language Keywords
The C language keywords represent the core of the language. With the C11
revision to the language, several new keywords have been added. They’re shown
with leading underscores in the following table:
_Alignas break float signed
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_Alignof case for sizeof
_Atomic char goto static
_Bool const if struct
_Complex continue inline switch
_Generic default int typedef
_Imaginary do long union
_Noreturn double register unsigned
_Static_assert else restrict void
_Thread_local enum return volatile
auto extern short while
Keep the following points in mind as you start programming in C:
Do not name any function or variable the same as a keyword.
You use only a few of the C language keywords in your code. Some of
them, you’ll probably never use.
Most of the work in your code is done by functions, not by keywords.
C Language Variable Types
Rather than make all your variables floats, it’s more efficient to examine the type
of data that’s stored and then choose an appropriate C variable type.
Type Value Range
_Bool 0 to 1
char –28 to 127
unsigned char 0 to255
short int –32,768 to 32,767
unsigned short int 0 to 65,535
int –2,147,483,648 to 2,147,483,647
unsigned int 0 to 4,294,967,295
long int –2,147,483,648 to 2,147,483,647
unsigned long int 0 to 4,294,967,295
float 1.17×10–38 to 3.40×1038
double 2.22×10–308 to 1.79×10308
Keep these C language variable type points in mind:
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7/20/2020 Beginning C Programming For Dummies Cheat Sheet
Ensure that you choose the proper variable type for the values you
need to store.
The _Bool type stores only two values, 0 and 1, which can represent
TRUE or FALSE or On or Off or any binary condition.
The char variable type stores character values, though it can also be
used to store tiny integers.
Integers, or whole numbers, are stored in the int variable types.
Any type of value, from the very large to the very small, and any
fractional values are stored in the float and double types.
Remember to use int values for functions that generate integers, such
as getchar(). It’s easy to assume that the function returns a char value
because of the function’s name.
C lacks a string variable type. Instead, an array of char variables is
used.
Other variable types include structures and pointers.
Common C Escape Sequences
When you cannot type characters into your string, use the escape sequences to
insert nonprintable characters into text strings, char variables, and arrays. Here are
common C escape sequences:
Characters What It Represents or Displays
a Bell (“beep!”)
b Backspace, non-erasing
f Form feed or clear the screen
n Newline
r Carriage return
t Tab
v Vertical tab
\ Backslash character
? Question mark
‘ Single quote
“
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Common C Conversion Characters
The printf() and scanf() functions use conversion characters as placeholders for
various values. Conversion characters are used to indicate a value when the
function runs in the final program.
Conversion
What It Displays
Character
%% The percent character (%)
%c A single character (char)
%d Integer value (short, int)
Floating-point value in scientific notation using a little E
%e
(float, double)
Floating-point value in scientific notation using a big E
%E
(float, double)
%f Floating-point value in decimal notation (float, double)
Substitutes %f or %e, whichever is shorter (float,
%g
double)
Substitutes %f or %E, whichever is shorter (float,
%G
double)
%i Integer value (short, int)
%ld Long integer value (long int)
%o Unsigned octal value, no leading zero
%p Memory location in hexadecimal (*pointer)
%s String (char *)
Unsigned integer (unsigned short, unsigned int, unsigned
%u
long)
Unsigned hexadecimal value, lower case (short, int,
%x
long)
Unsigned hexadecimal value, capital letters (short, int
%X
long)
The Order of Precedence in C
The order of precedence determines which operators act upon a value first. When
crafting statements, know the order of precedence to ensure that the program does
what you intend.
Operator(s) Category Description
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! Unary Logical not; associativity goes right to left
++ — Unary Increment, decrement, read from right to left
*/% Math Multiplication, division, modulo
+– Math Addition, subtraction
<< >> Binary Shift left, shift right
Less than, greater than, less than or equal to, greater
< > <= >= Comparison than or
equal to
== != Comparison Is equal to, not equal to
& Binary And
^ Binary Exclusive or (XOR)
| Binary Or
&& Logical And
|| Logical Or
?: Comparison Weird if thing; associativity goes right to left
Variable assignment operator, including the +=, *=,
= Assignment and all
assignment operators
The comma separates items in a for
, (None)
statement; precedence from left to right
The order of precedence can be overridden by using parentheses. Simply enclose
within a set of parentheses the part of the equation that you want executed first.
That part is executed first no matter what the priority is.
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