Alex
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C语言程序设计基础
数据类型
计算机学院 杨已彪
yangyibiao@nju.edu.cn
Review
Functions
Function Definition
Function Declaration
Arrays as Parameters
Pass by Value
Overview
</br> </br> </br>
(Basic) Data Types
Two Major Reasons
Architectures May Vary
Finite vs. Infinite
Object
Object Types Function Types
Data Types
The **type** of a variable determines
-
the set of values it may take on and
-
what operations can be performed on them.
int char bool (_Bool) double
[ ]
Integral Types (size.c)
-
(unsigned) short (int)
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unsigned int
-
unsigned long (int)
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unsigned long long (int)
Integral Types
-
(unsigned) short (int)
-
unsigned int
-
unsigned long (int)
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unsigned long long (int)
Integral Types (int-limits.c)
-
(unsigned) short (int)
-
unsigned int
-
unsigned long (int)
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unsigned long long (int)
Integral Types (exact-width.c)
int8_t int16_t int32_t int64_t
stdint.h
Signed and Unsigned (unsigned.c)
Be careful when MIXING signed and unsigned types.
Signed and Unsigned (sizet.c)
typedef
typedef unsigned __int64 size_t
#define _ _int64 long long
typedef long long time_t
char (char.c)
Use char only for representing characters.
Do NOT assume signed char or unsigned char.
Overflow
(unsigned-wrap.c for-unsigned.c unsigned-wrap-fix.c)
无符号整数运算中没有溢出, 取而代之的是**回绕 (wrap)**现象
Overflow
(signed-overflow-fix.c)
有符号整数运算中发生溢出, 程序的行为是**未定义的**
Implicit Conversion
(implicit-conversion.c)
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算术表达式、逻辑表达式 (先做整值提升 )
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定义初始化、赋值 (类型转换)
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函数调用时 (类型转换)
-
函数返回时 (类型转换)
Be careful about narrowing conversions!!!
Implicit Conversion
Integer promotions (integer-promotion.c)
Integer conversion rank (Section 7.4.3)
Usual arithmetic conversions (Section 7.4.1)
Explicit Conversion
(explicit-conversion.c)
(type) expression
Floating-point Numbers
(float-limits.c)
-
float (F)
-
double
-
long double (L)
"Floating-point Arithmetic is Hard."
(Section 23.1 float.h)
"Many applications don't need floating-point arithmetic at all."
Use math.h (Section 23.3) whenever possible.
IEEE 754
$24 \; (\approx 6) \qquad\qquad 53 \; (\approx 16)$
What is a subnormal floating point number? @ stackoverflow
implicit-conversion.c
sum-product.c loop.c compare.c
