Precompiled Header Files

	Chapter 14 - Advanced Programming Topics
	Visual C++ 6: The Complete Reference
	Chris H. Pappas and William H. Murray, III

Copyright 1998 The McGraw-Hill Companies

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	LIMITS.H and FLOAT.H

	The ANSI C committee requires that all C compilers document the system-dependent ranges of integer and floating-point types in order to help you write portable code. Table 14-2 contains a listing of the ANSI C-required integral definitions found in the LIMITS.H header file.

	Table 14-2: Values defined in LIMITS.H (ANSI C)

	Defined Type

Size

Description

	#define CHAR_BIT

8

Number of bits in a char

	#define CHAR_MAX

SCHAR_MAX

Maximum char value

	#define CHAR_MIN

SCHAR_MIN

Minimum char value

	#define INT_MAX

2147483647

Maximum (signed) int value

	#define INT_MIN

(-2147483647 – 1)

Minimum (signed) int value

	#define LONG_MAX

2147483647L

Maximum (signed) long value

	#define LONG_MIN

(-2147483647L – 1)

Minimum (signed) long value

	#define SCHAR_MAX

127

Maximum signed char value

	#define SCHAR_MIN

(-128)

Minimum signed char value

	#define SHRT_MAX

32767

Maximum (signed) short value

	#define SHRT_MIN

(-32768)

Minimum (signed) short value

	#define UCHAR_MAX

0xff

Maximum unsigned char value

	#define UINT_MAX

0xffffffff

Maximum unsigned int value

	#define ULONG_MAX

0xffffffffUL

Maximum unsigned long value

	#define USHRT_MAX

0xffff

Maximum unsigned short value

	Program code can use these ranges to make certain that data will fit in the specified data type. For example, a VAX integer may be 4 bytes, while an older DOS-based integer is only 2. To solve this problem, the following code might be used:

	if (PROGRAM_NEEDED_MAX > INT_MAX)  pvoid = new llong_storage; else  pvoid = new iinteger_storage;

	Table 14-3 shows the ANSI C-required floating-point definitions.

	Table 14-3: Values Defined in FLOAT.H(ANSI C)

	Definition

Value

Comment

	#define FLT_RADIX

2

Exponent radix

	#define FLT_ROUNDS

1

Addition rounding: near

	smallest such that 1.0+FLT_EPSILON != 1.0 #define FLT_EPSILON

1.192092896e-07F

	smallest such that 1.0+DBL_EPSILON != 1.0 #define DBL_EPSILON

2.2204460492503131e-016

	smallest such that 1.0+LDBL_EPSILON != 1.0 #define LDBL_EPSILON

DBL_EPSILON

	#define FLT_DIG

6

# of decimal digits of precision

	#define DBL_DIG

15

# of decimal digits of precision

	#define LDBL_DIG

DBL_DIG

# of decimal digits of precision

	#define FLT_MIN

1.175494351e-38F

Min positive val

	#define DBL_MIN

2.2250738585072014e-308

Min positive val

	#define LDBL_MIN

DBL_MIN

Min pos val

	#define FLT_MIN_EXP

(-125)

Min binary exponent

	#define DBL_MIN_EXP

(-1021)

Min binary exponent

	#define LDBL_MIN_EXP

DBL_MIN_EXP

Min binary exponent

	#define FLT_MIN_10_EXP

(-37)

Min decimal exponent

	#define DBL_MIN_10_EXP

(-307)

Min decimal exponent

	#define LDBL_MAX_10_EXP

DBL_MIN_10_EXP

Max decimal exponent

	#define FLT_MAX

3.402823466e+38F

Max value

	#define DBL_MAX

1.7976931348623158e+308

Max value

	#define LDBL_MAX

DBL_MAX

Max value

	#define FLT_MAX_EXP

128

Max binary exponent

	#define DBL_MAX_EXP

1024

Max binary exponent

	#define LDBL_MAX_EXP

DBL_MAX_EXP

Max binary exponent

	#define FLT_MAX_10_EXP

38

Max decimal exponent

	#define DBL_MAX_10_EXP

308

Max decimal exponent

	#define LDBL_MAX_10_EXP

DBL_MAX_10_EXP

Max decimal exponent

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