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MODULE 2

C AND C++ PROGRAM CONSTRUCT

AND BASIC DATA TYPES 1

My Training Period: xx hours

ANSI C refers to ISO/IEC C. The source code for this Module is: C & C++ source codes and the practice worksheets: C & C++ basic data types and the C & C++ standard input, scanf()/scanf_s().

The C/C++ programming skills that supposed to be acquired:

Able to understand the basic structure of the C / C++ program.
Able to understand and use the basic data types.
Able to recognize and use the keywords and variables.
Able to understand and use the constant, character and escape sequence.
Able to understand and use the C typecasting/promotion.

2.1 What Is A Program?

C / C++ programs consist of functions (routines/procedures/methods), one of which must be main() for execution point to start. Every C / C++ program begins execution at the main() function.

2.2 Keywords / Reserved Words

The keywords used in C/C++ have special meaning to the compiler. The programmer can’t use these words for identifiers such as variable names. The following table is a list of keywords used in ANSI C.

Keyword	Description
auto	An automatic storage class for automatic variable. Normally not explicitly used.
break	Used to force an immediate exit from while, for, do loops and switch-case statement.
case	A label used together with switch statement for selection.
char	A single byte data type, capable holding one character in the character set.
const	A qualifier used to declare variable to specify that its value will not be changed.
continue	Related to break statement, causes the next iteration of the enclosing for, while or do loop to begin. Applies only to loops, not to switch statement.
default	An optional label used together with case label. When there is no case expression matched, default label expression will be executed.
do	Used in do-while loop, repetition where the test condition is at the end of the loop body.
double	A double-precision floating point.
elif	#elif. Preprocessor statement for else-if.
else	Used together with if (if-else) for conditional execution.
endif	#endif. Preprocessor statement for end-if.
enum	Used in declaring enumeration constant. Enumeration is a list of constant integer values.
extern	External storage class. External to all function or globally accessible variable. Variable declared with extern can be accessed by name by any function.
float	Used when declaring floating-point data type.
for	Used in the repetition loop.
goto	A program control statement for branching/jumping to.
if	Used for conditional execution, standalone or with else. #if used for conditional inclusion of the preprocessor directive.
ifdef	#ifdef, if defined; test whether a name is defined.
ifndef	#ifndef, if not defined; test whether a name is not defined.
int	An integer data type, the size of normal integers.
long	A qualifier (long and short) applied to basic data types. short – 16 bits, long-32 bits, int either 16 or 32 bits.
register	Another storage class specifier. Used to advise the compiler to place the variables in machine’s processor register instead of machine’s memory but it is not a mandatory for the compiler.
return	Used to return a value from the called function to its caller. Any expression can follow return. The calling function is free to ignore the returned value and can be no expression after return (no value is returned). For main(), return will pass to system environment, operating system if there is no error.
short	A qualifier (long and short) applied to basic data types. short – 16 bits, long-32 bits, int either 16 or 32 bits.
signed	A qualifier may be applied to char or any integer. For example, signed int. Including the positive and negative integers. For example, integer equivalent range for signed char is -128 and 127 (2’s complement machine).
sizeof	An operator. Shows the number of bytes (occupied or) required to store an object of the type of its operand. The operand is either an expression or a parenthesized type name.
static	A storage class specifier. Local variables (internal variables) that retain their values throughout the lifetime of the program. Also can be applied to external variables as well as functions. Functions declared as static, its name is invisible outside of the file in which it is declared. For an external variables or functions, static will limit the scope of that objects to the rest of the source file being compiled.
struct	A structure specifier for an object that consist a sequence of named members of various types.
switch	Used in a selection program control. Used together with case label to test whether an expression matches one of a member of case’s constant integer and branches accordingly.
typedef	Used to create new data type name.
union	A variable that may hold (at different time) objects of different types and sizes. If at the same time, use struct.
unsigned	A qualifier may be applied to char or any integer. For example, unsigned int. Including the positive integers or zero. For example, integer equivalent range for unsigned char is 0 and 255.
void	Data type that specifies an empty set of values or nonexistence value but pointers (pointers to void) may be assigned to and from pointers of type void *.
volatile	A qualifier used to force an implementation to suppress optimization that could otherwise occur.
while	Used for conditional loop execution. Normally together with the do.
Table 2.1: ANSI C Keywords

The following table is a list of C++ keywords; most of the keywords will be used in C++ Tutorial.

Keywords	Brief descriptions
asm	Using or inserting assembly language in C++, refer to your compiler documentation support.
catch	Exception handling generated by a throw keyword.
bool	To declare Boolean logic variables; that is, variables which can be either true or false.
class	Define a new class then objects of this class can be instantiated.
const_cast	To add or remove the const or volatile modifier from a type.
delete	Destroy an object in memory dynamically, created by using keyword new.
dynamic_cast	Convert a pointer or reference to one class into a pointer or reference to another class using run time type information (rtti). (Converts a pointer to a desired type.
explicit	Used to avoid a single argument constructor from defining an automatic type conversion in class declaration.
false	The Boolean value of "false".
friend	Declare a function or class to be a friend of another class providing the access of all the data members and member function of a class.
inline	Asking the compiler that certain function should be generated or executed inline instead of function call.
mutable	The mutable keyword overrides any enclosing const statement. A mutable member of a const object can be modified.
namespace	Keyword used to create a new scope.
new	Dynamically allocate a memory object on a free store, that is an extra memory that available to the program at execution time and automatically determine the object's size in term of byte.
operator	Declare an overloaded operator.
private	A class member accessible to member functions and friend functions of the private member's class.
protected	protected members may be accessed by member functions of derived classes and friends of derived classes.
public	A class member accessible to any function.
reinterpret_cast	Replaces casts for conversions that are unsafe or implementation dependent.
`static_cast`	Converts types between related types.
template	Declare how to construct class or function using variety of types.
this	A pointer implicitly declared in every non-static member function of a class. It points to the object for which this member function has been invoked.
throw	Transfer control to an exception handler or terminate program execution if appropriate handler cannot be located.
true	The Boolean value of "true".
try	Creates a block that containing a set of statements that may generate exceptions, and enables exception handling for any exceptions generated (normally used together with throw and catch).
typeid	Gets run-time identification of types and expressions.
typename	Used to qualify an identifier of a template as being a type instead of a value.
using	Used to import a namespace into the current scope.
virtual	Declare a virtual function.
wchar_t	Used to declare wide character variables.
Table 2.2: C++ Keywords

The following are C keywords defined by ISO/IEC 9899:1999 (C99).

auto	break	case	char	const	continue	default	do	double	else	enum
extern	float	for	goto	if	inline	int	long	register	restrict	return
short	signed	sizeof	static	struct	switch	typedef	union	unsigned	void	volatile
while	_Bool	_Complex	_Complex	_Imaginary	...

One way to master C/C++ programming is to master the keywords and their usages :o). From time to time when there are new C/C++ standard, new keywords should be introduced and some will be removed.

2.3 C/C++ Identifiers

Name that simply references to memory locations, which can hold values (data).
Are formed by combining letters (both upper and lowercase), digits (0–9) and underscore ( _ ).
Rules for identifier naming are:

The first character of an identifier must be a letter, an underscore ( _ ) also counts as a letter.

The blank or white space character is not permitted in an identifier.

Can be any length. Internal identifier (do not have the external linkage) such as preprocessor macro names at least the first 31 characters are significant, also implementation dependent.

Reserved words/keywords and characters such as main and # also cannot be used.

2.4 C/C++ Variables

Identifier that value may change during the program execution.
Every variable stored in the computer’s memory has a name, a value and a type.
All variable in a C/C++ program must be declared before they can be used in the program.
A variable name in C/C++ is any valid identifier, and must obey the rules mentioned above.
Initializing a variable means, give a value to the variable, that is the variable’s initial value and can be changed later on.
Variable name are said to be lvalue (left value) because they can be used on the left side of an assignment operator.
Constant are said to be rvalue (right value) because they only can be used on the right side of an assignment operator. For example:

x = 20;

x is lvalue, 20 is rvalue.

The evaluation is done from right to left, that is right value to left value.
Note that lvalue can also be used as rvalue, but not vice versa.
Notation used in C/C++ can be Hungarian Notation or CamelCase Notation. The information for these notations can be found in C/C++ Notations.
The following shows variable declaration examples:

int x, y, z;

short number_one;

long Type0fCar;

unsigned int positive_number;

char Title;

float commission, yield;

The variable declaration general form:

data_type variable_list;

Note the blank space.

The following shows declaring and initializing variables examples:

int m, n = 10;

char * ptr = "TESTING";

float total, rate = 0.5;

char user_response = ‘n’;

char color[7] = "green";

Or declare and initialize:

int m, n;

float total, rate;

char user_response;

char color[7];

n = 20;

rate = 4.5;

user_response = ‘n’;

color = "green";

2.5 Basic Data types

Why we need to learn data types? Every variable used in program hold data, and every data must have their own type. It is the way how we can ‘measure’ the variable’s data value as exist in the real world. Further more by knowing the data range, we can use data efficiently in our program in term of memory management (storage allocation) aspects.
For example, no need for us to reserve a lot of storage space such as a long data type if we just want to store a small amount of data, let say, int data type.
Every data in C/C++ has their own type. There are basic data type and derived data type. This Module deals with basic data type.
There are two kinds of basic data type: integral (integer value) and floating (real number). char data type classified in integral type.
Derived data types will be presented in another Module. Derived data type including the aggregate data type is constructed from basic data type such as arrays, functions, pointers, structures, unions and other user defined data types. Basic data type (int, char and float) and their variation are shown in Table 2.3. 2.4 and 2.5.

Data type	Keyword	Bits	Range
integer	int	16	-32768 to 32767
long integer	long	32	-4294967296 to 4294967295
short integer	short	8	-128 to 127
unsigned integer	unsigned	16	0 to 65535
character	char	8	0 to 255
floating point	float	32	approximately 6 digits of precision
double floating point	double	64	approximately 12 digits of precision
Table 2.3: Basic data type

The following tables list the sizes and resulting ranges of the data types based on IBM PC compatible system. For 64 bits, the size and range may not valid anymore☺.

Type	Size (bits)	Range	Sample applications
unsigned char	8	0 to 255	Small numbers and full PC character set
char	8	-128 to 127	Very small numbers and ASCII characters
enum	16	-32,768 to 32,767	Ordered sets of values
unsigned int	16	0 to 65,535	Larger numbers and loops
short int	16	-32,768 to 32,767	Counting, small numbers, loop control
int	16	-32,768 to 32,767	Counting, small numbers, loop control
unsigned long	32	0 to 4,294,967,295	Astronomical distances
long	32	-2,147,483,648 to 2,147,483,647	Large numbers, populations
float	32	3.4^-1038 to 3.4¹⁰³⁸	Scientific (7-digit precision)
double	64	1.7^-10308 to 1.7¹⁰³⁰⁸	Scientific (15-digit precision)
long double	80	3.4^-104932 to 1.1¹⁰⁴⁹³²	Financial (18-digit precision)
near pointer	16	Not applicable	Manipulating memory addresses
far pointer	32	Not applicable	Manipulating addresses outside current segment
Table 2.4: C++ 16-bit data types, sizes, and ranges

Type	Size (bits)	Range	Sample applications
unsigned char	8	0 to 255	Small numbers and full PC character set
char	8	-128 to 127	Very small numbers and ASCII characters
short int	16	-32,768 to 32,767	Counting, small numbers, loop control
unsigned int	32	0 to 4,294,967,295	Large numbers and loops
int	32	-2,147,483,648 to 2,147,483,647	Counting, small numbers, loop control
unsigned long	32	0 to 4,294,967,295	Astronomical distances
enum	32	-2,147,483,648 to 2,147,483,647	Ordered sets of values
long	32	-2,147,483,648 to 2,147,483,647	Large numbers, populations
float	32	3.4 ^-1038 to 1.7¹⁰³⁸	Scientific (7-digit) precision)
double	64	1.7 ^-10308 to 3.4¹⁰³⁰⁸	Scientific (15-digit precision)
long double	80	3.4 ^-104932 to 1.1¹⁰⁴⁹³²	Financial (18-digit precision)
Table 2.5: C++ 32-bit data types, sizes, and ranges

We are very familiar with integer constants that are the base 10 numbers, 0 – 9. There are other bases such as 16, 8 and 2 numbers that we will encounter when learning programming.
Octal integer constants must start with 0 followed by any combination of digits taken from 0 through 7. For examples:

0 07 0713 // represent octal numbers

Hexadecimal integer constants must start with 0x or 0X (capital hexadecimal) followed by any combination of digits taken from 0 through 9 and uppercase letters A through F. For examples:

0x 0x8 0XADC 0X2FD // represent hexadecimal numbers

The literal data-type qualifiers bring different means for same constant data. For example:

-    75 mean the integer 75, but 75L represents the long integer 75.

-    75U means the unsigned integer 75.

-    75UL means the unsigned long integer 75.

-    4.12345 mean the double value 4.12345, but 4.12345F represents the float value 4.12345.

The The following table lists the suffix that defined by ISO, also implemented by Microsoft. You can find their usages in variable declaration, the standard input function (scanf()/scanf_s()) and standard output function, printf()/printf_s()). You will find the examples in the C lab worksheet practice.

Suffix	Decimal Constant	Octal or Hexadecimal Constant
none	int long int long long int	int unsigned int long int unsigned long int long long int unsigned long long int
u or U	unsigned int unsigned long int unsigned long long int	unsigned int unsigned long int unsigned long long int
l or L	long int long long int	long int unsigned long int long long int unsigned long long int
Both u or U and l or L	unsigned long int unsigned long long int	unsigned long int unsigned long long int
ll or LL	long long int	long long int unsigned long long int
Both u or U and ll or LL	unsigned long long int	unsigned long long int
Table 2.X: suffix that defined by ISO

C & C++ programming tutorials

Further C and C++ reading and digging:

The ASCII, EBCDIC and UNICODE character sets reference Table can be found here: Character sets Table.
Check the best selling C/C++ books at Amazon.com.

|< Introduction | Main | Basic Data Type 2 >| Site Index | Download |

Program Structure & Basic Data Type: Part 1 | Part 2 | Part 3 | Part 4 |

|< Introduction | Main | Basic Data Type 2 >| Site Index | Download |

MODULE 2

C AND C++ PROGRAM CONSTRUCT

AND BASIC DATA TYPES 1

My Training Period: xx hours

The C/C++ programming skills that supposed to be acquired:

Able to understand the basic structure of the C / C++ program.

Able to understand and use the basic data types.

Able to recognize and use the keywords and variables.

Able to understand and use the constant, character and escape sequence.

Able to understand and use the C typecasting/promotion.

2.1 What Is A Program?

2.2 Keywords / Reserved Words

2.3 C/C++ Identifiers

2.4 C/C++ Variables

2.5 Basic Data types

Keyword

Bits

Further C and C++ reading and digging:

|< Introduction | Main | Basic Data Type 2 >| Site Index | Download |

Program Structure & Basic Data Type: Part 1 | Part 2 | Part 3 | Part 4 |