Code Generation Conventions

Arithmetic Data Types

The compiler implements the standard C data types as follows:

doubles and long doubles are 8 bytes in length and are aligned on an 8-byte (doubleword) boundary. floats are 4 bytes in length and are aligned on a 4-byte boundary.
longs and ints , both signed and unsigned, are 4 bytes in length and are aligned on a 4-byte (fullword) boundary.
shorts and unsigned shorts are 2 bytes in length and are aligned on a 2-byte (halfword) boundary.
both signed and unsigned char are 1 byte (8 bits) in length and are aligned on byte boundaries.
A structure or union is aligned according to the strictest alignment requirement of any of its members (including other structures or unions). This rule is applied recursively. Note that if you specify the bytealign compiler option, most data items, including all those in structures, are generated with only character alignment.

All data types use the normal 370 representation. Data Type Characteristics summarizes the characteristics of the arithmetic data types.

Data Type Characteristics
Type Length Alignment Range

char 1 byte 0 to 255 (EBCDIC character set)

signed char 1 byte -- 128 to 127

unsigned char 1 byte 0 to 255 (EBCDIC character set)

short 2 halfword -- 32768 to 32767

unsigned short 2 byte 0 to 65535

int 4 word -- 2147483648 to 2147483647

long 4 word -- 2147483648 to 2147483647

unsigned 4 word 0 to 4294967295

float 4 word =/ -- 5.4E -- 79 to =/ -- 7.2E75

double 8 doubleword =/ -- 5.4E -- 79 to =/ -- 7.2E75

long double 8 doubleword =/ -- 5.4E -- 79 to =/ -- 7.2E75

char unsigned char defines an 8-bit unsigned integer

signed char short short int defines an 8-bit signed integer
defines a 16-bit signed integer

unsigned short unsigned short int defines a 16-bit unsigned integer

int long long int defines a 32-bit signed integer

unsigned unsigned int unsigned long int defines a 32-bit unsigned integer

float defines a 32-bit signed floating-point number in the standard 370 representation, that is, a sign bit, a 7-bit biased hexadecimal exponent, and a 24-bit fractional part. The exponent bias is 64. All constants and results generated by compiled code are normalized (except for constants specified in hexadecimal notation). This representation is equivalent to approximately 6 or 7 decimal digits of precision

double long double defines a 64-bit signed floating-point number in the standard 370 representation, that is, a sign bit, a 7-bit biased hexadecimal exponent, and a 56-bit fractional part. The exponent bias is 64. All constants and results generated by compiled code are normalized (except for constants specified in hexadecimal notation). This representation is equivalent to approximately 16 or 17 decimal digits of precision

***Data Type Characteristics***
Type	Length	Alignment	Range
`char`	1	byte	0 to 255 (EBCDIC character set)
`signed char`	1	byte	-- 128 to 127
`unsigned char`	1	byte	0 to 255 (EBCDIC character set)
`short`	2	halfword	-- 32768 to 32767
`unsigned short`	2	byte	0 to 65535
`int`	4	word	-- 2147483648 to 2147483647
`long`	4	word	-- 2147483648 to 2147483647
`unsigned`	4	word	0 to 4294967295
`float`	4	word	=/ -- 5.4E -- 79 to =/ -- 7.2E75
`double`	8	doubleword	=/ -- 5.4E -- 79 to =/ -- 7.2E75
`long double`	8	doubleword	=/ -- 5.4E -- 79 to =/ -- 7.2E75
`char unsigned char`	defines an 8-bit unsigned integer
`signed char short short int`	defines an 8-bit signed integer defines a 16-bit signed integer
`unsigned short unsigned short int`	defines a 16-bit unsigned integer
`int long long int`	defines a 32-bit signed integer
`unsigned unsigned int unsigned long int`	defines a 32-bit unsigned integer
`float`	defines a 32-bit signed floating-point number in the standard 370 representation, that is, a sign bit, a 7-bit biased hexadecimal exponent, and a 24-bit fractional part. The exponent bias is 64. All constants and results generated by compiled code are normalized (except for constants specified in hexadecimal notation). This representation is equivalent to approximately 6 or 7 decimal digits of precision
`double long double`	defines a 64-bit signed floating-point number in the standard 370 representation, that is, a sign bit, a 7-bit biased hexadecimal exponent, and a 56-bit fractional part. The exponent bias is 64. All constants and results generated by compiled code are normalized (except for constants specified in hexadecimal notation). This representation is equivalent to approximately 16 or 17 decimal digits of precision

Note that in contrast to the signed integer representations, negative floating-point values are not represented in two's complement notation; positive and negative numbers differ only in the sign bit. Also note that there are multiple representations of 0; any value that has a 0 fractional part is treated as 0 by the IBM 370 floating-point instructions, regardless of the exponent value.

Code that checks float or double objects for 0 by means of type punning (that is, examining the objects as if they were int or some other nonfloating-point type) may assume (falsely) negative 0 not to be 0.

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