06-Binary, bitwise operations, arrays, and strings

One, the binary

1. What is a binary

* is a way of counting, the representation of a numeric value

2. Binary

* Features: only 0 and 1, every 2 into 1

* Writing format:0b or 0b start

* Application: Binary instruction \ binary file, variable in memory is binary storage

3. octal

* Features:0~ 8 in 1

* Writing format:0 start

4. hex

* Features:0~f, 1 in every

* Writing format:0x or 0x start

Second, bitwise operations

1. & Press at

1> features

Only the corresponding two binaries are 1, the result bit is 1, otherwise 0.

2> Law

Binary, with 1- phase & to remain in place, and 0 -phase & is 0

2. | bitwise OR

1> features

As long as the corresponding two binaries have 1 for 1 , the result is 1, otherwise 0.

3. ^ bitwise XOR or

1> features

When the corresponding binary is different (not the same), the result is 1, otherwise 0

2> Law

* The result of the same integer ^ is 0. For example 5^5=0

* multiple integers ^ results are independent of order. For example 5^6^7=5^7^6

* thus concludes:A^b^a = b

4. ~ Take back

The binary of Integer A is reversed, and the sign bit is reversed (0 to 1, 1 to 0)

5. << shift left

All the binary of the integer A is left n bits, the high is discarded, and the low is 0.

6. >> Move right

shift all the binary in integer A to the right n bits, keeping the sign bit constant.

three, array

1. features of the array

* only one type of data can be stored, such as an array of type int , An array of type float

* data stored inside is called " element "

2. format

Element type array name [ number of elements ];

Like what:

int ages[3];

3. Initialize

int a[3] = {1,2,3}; int a[] = {1,5,%}; int a[5] = {[2]=6,+//  Indicates starting from subscript 2 initialization, if the subscript is exceeded, there will be a warning, the runtime will not error int//  error

Four, String

1. Initialization of strings

* "123" is actually by '1','2','3',' \0 ' composition

2. commonly used string processing functions

Strlen ()

06-Binary, bitwise operations, arrays, and strings