Learning Object-C from scratch --- the fourth day (2), object-c --- the fourth day

Learning Object-C from scratch --- the fourth day (2), object-c --- the fourth day

I have been busy with the company recently and stopped for a few days. Learning is more important than sticking to it.

Today, I will explain how to use Object-C data types and expressions.

1. float Type

//// Main. m // Demo3 /// Created by lee on 14/11/3. // Copyright (c) 2014 lee. all rights reserved. // # import <Foundation/Foundation. h> int main (int argc, const char * argv []) {@ autoreleasepool {// General float Type float f = 0.01; NSLog (@ "f is: % f ", f); // float e = 1.7e4; NSLog (@ "e is: % f", e); NSLog (@ "e is: % e", e ); // % g use float g = 100.00; NSLog (@ "g is: % g", g); // hexadecimal float s = 0x0. 3p10; NSLog (@ "s id: % f", s);} return 0 ;}

The 1.1 float type is used to store values that contain decimal places. The conversion symbol % f is usually used in NSLog.

The 1.2 float type can also be expressed by scientific notation. For example, 1.2e4 represents the 4 power of 1.2 multiplied by 10. Note: The values before e are the ending number, and the values after e are the exponent.

1.3 The explicit values of scientific computing are represented by the format character % e in NSLog.

1.4 The hexadecimal floating point number is composed of one or more hexadecimal numbers plus the leading 0x or 0X plus the p or P plus the signed Binary Index. For example, 0x0. 3p10 indicates that 3/16 is multiplied by the 10th power of 2.

2. double Type

2.1 double type can store more than twice the ending count float. Most computers use 64-bit to represent the double value.

2.2 Unless specified, Object-C defines all floating point constants as double by default.

2.3 add f or F to the number of float constants, for example, float f = 1.23f;

2.4 double type: % f, % 3, % g. The usage is the same as that of float.

3. char type

3.1 char is used to store a single character and put the character in a pair of single quotes, such as 'A', ';', and '0 '.

3.2 '0' is not the same as the number 0.

3.3 '\ n' is also a valid character constant.

Common Data Types of Object-C:

//// Main. m // Demo4 /// Created by lee on 14/11/3. // Copyright (c) 2014 lee. all rights reserved. // # import <Foundation/Foundation. h> int main (int argc, const char * argv []) {@ autoreleasepool {int integerVar = 100; float floatingVar = 300.12; double doubleVar = 8.44e + 11; char charVar = 'a'; NSLog (@ "integerVar = % I", integerVar); NSLog (@ "floatingVar = % f", floatingVar ); NSLog (@ "doubleVar = % e", doubleVar); NSLog (@ "doubleVar = % g", doubleVar); NSLog (@ "char = % c", charVar );} return 0;} output result: 23:58:11. 220 Demo4 [535: 24056] integerVar = 1002014-11-03 23:58:11. 221 Demo4 [535: 24056] floatingVar = 300.1199952014-11-03 23:58:11. 221 Demo4 [535: 24056] doubleVar = 8.44366e + 112014-11-03 23:58:11. 221 Demo4 [535: 24056] doubleVar = 8.44e + 112014-11-03 23:58:11. 221 Demo4 [535: 24056] char = AProgram ended with exit code: 0

 

How to Learn object-c

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