third chapter
type of data
128U no sign number 128
1024U unsigned number 1024 u case
1L long shape 1
8LU no symbol Long type 8
Vertical tab / V
Wide character wchar_t l'a '
variable
The object name generally uses lowercase letters, for example, we tend to write index without writing index.
Wood as a type name and INDEX is generally seen as a constant value usually defined with a pre-processor indicator #define
. Identifier generally uses a helpful name - that the name of the prompt can be prompted on the usage in the program.
ON_LOAN or SALARY is what should be written as a Table or TBL This is purely style problem is not correct.
problem
For a plurality of words composed, it is generally generally plus a downline or embedding between each word.
The first letter of the word is, for example, will be written into student_loan or studentloan instead of
StudentLoan I have listed all three forms of people in all three forms.
Objectorientedbackground likes people with C or process background with uppercase letters
C_OR_PROCEDURAL_BACKGROUND The next line is again explained using ISA ISA or IS_A
Just a style problem and correct or not
A simple definition specifies the type and identifier of the variable. It does not provide an initial value if a variable is defined within the full Law Global Scope, and the system guarantees the initial value of 0
If the variable is defined in the local domain local scope or dynamically allocated by the New Expression, the system does not provide initial value 0 these objects are called uninited uninitialized.
The object that is not initialized is not no value but its value is undefined undefined
C supports two forms of initialization first form is an explicit syntax form using assignment operators.
INT IVAL = 1024;
String Project = "Fantasia 2000";
In the implicit form, the initial value is placed in parentheses.
INT IVAL (1024);
String Project ("Fantasia 2001");
Pointer type
In the example below, LP is a pointer to the LONG type object and LP2 is a long-type data object not a pointer.
Long * LP, LP2;
When the programmer wanted to define the second string pointer, he will correctly modify the definition.
// 喔: PS2 is not a string pointer
String * ps, ps2;
VOID * Type pointer it can be assigned the value of the address value of any data pointer type to be assigned to it
// OK: void * can hold any address value of any pointer type
Void * PV = Pi;
PV = Pd;
Pointer to pointers, examples
#include
Using
Namespace
STD;
Int main () {
INT A = 20;
INT * P = & A;
Cout <<
"A:" << a << Endl <<
"* P:" << * p << endl;
INT ** PP = & P;
// & p point to the address of the pointer
Cout <<
"** PP:" << ** PP << Endl;
// Double solution reference
Return 0;
}
Pointer plus 2 means that the address value held by the pointer adds the length of the type of two objects, for example, suppose a char is one byte an int is 4 byte double is 8 bytes. So pointers
Plus 2 is to increase the address value of 2 8 or 16 is completely dependent on the type of pointer is Char Int or Double
String type
Convert String as a C-Style string:
Const char * str = string1.c_str ()
^^^^^
Const limit modifier
Const int buffsize = 512 // Buffer size prevents this error:
IF (bufsize = 0) {...}
Const Double * CPTR;
CPTR is a pointer to a CONST object to a Double type. We can read this definition from right left.
CPTR is a pointer to the Double type to be defined in this, this medium is subtle in the CPTR
It is not a constant that we can re-assign CPTR to point to different objects but cannot modify the object pointing to the CPTR.
Can't modify the value points to the Const pointer
Char * str = "llll";
Const char * p = STR;
* p = '4'; // incorrect
Reference type
INT IVAL = 1024;
INT * PI = & IVAL;
// ok: refptr is a reference to a pointer
INT * & PTRVAL2 = Pi;
Once the reference has been defined, you can no longer point to other objects.
Double DVAL = 3.14159;
// Only for const references is legal
Const Int & IR = 1024;
Const Int & IR2 = DVAL;
Const Double & DR = DVAL 1.0;
Boolean type enumeration type
ENUM ENUMTEST {a, b, c, d}
ENUM ENUMTEST2 {a = 1, b = 3}
>> END << //
