我想了解这种转换是如何发生的。
http://www8.cs.umu.se/~isak/Snippets/a2e.c
/*
** ASCII <=> EBCDIC conversion functions
*/
static unsigned char a2e[256] = {
0, 1, 2, 3, 55, 45, 46, 47, 22, 5, 37, 11, 12, 13, 14, 15,
16, 17, 18, 19, 60, 61, 50, 38, 24, 25, 63, 39, 28, 29, 30, 31,
64, 79,127,123, 91,108, 80,125, 77, 93, 92, 78,107, 96, 75, 97,
240,241,242,243,244,245,246,247,248,249,122, 94, 76,126,110,111,
124,193,194,195,196,197,198,199,200,201,209,210,211,212,213,214,
215,216,217,226,227,228,229,230,231,232,233, 74,224, 90, 95,109,
121,129,130,131,132,133,134,135,136,137,145,146,147,148,149,150,
151,152,153,162,163,164,165,166,167,168,169,192,106,208,161, 7,
32, 33, 34, 35, 36, 21, 6, 23, 40, 41, 42, 43, 44, 9, 10, 27,
48, 49, 26, 51, 52, 53, 54, 8, 56, 57, 58, 59, 4, 20, 62,225,
65, 66, 67, 68, 69, 70, 71, 72, 73, 81, 82, 83, 84, 85, 86, 87,
88, 89, 98, 99,100,101,102,103,104,105,112,113,114,115,116,117,
118,119,120,128,138,139,140,141,142,143,144,154,155,156,157,158,
159,160,170,171,172,173,174,175,176,177,178,179,180,181,182,183,
184,185,186,187,188,189,190,191,202,203,204,205,206,207,218,219,
220,221,222,223,234,235,236,237,238,239,250,251,252,253,254,255
};
static unsigned char e2a[256] = {
0, 1, 2, 3,156, 9,134,127,151,141,142, 11, 12, 13, 14, 15,
16, 17, 18, 19,157,133, 8,135, 24, 25,146,143, 28, 29, 30, 31,
128,129,130,131,132, 10, 23, 27,136,137,138,139,140, 5, 6, 7,
144,145, 22,147,148,149,150, 4,152,153,154,155, 20, 21,158, 26,
32,160,161,162,163,164,165,166,167,168, 91, 46, 60, 40, 43, 33,
38,169,170,171,172,173,174,175,176,177, 93, 36, 42, 41, 59, 94,
45, 47,178,179,180,181,182,183,184,185,124, 44, 37, 95, 62, 63,
186,187,188,189,190,191,192,193,194, 96, 58, 35, 64, 39, 61, 34,
195, 97, 98, 99,100,101,102,103,104,105,196,197,198,199,200,201,
202,106,107,108,109,110,111,112,113,114,203,204,205,206,207,208,
209,126,115,116,117,118,119,120,121,122,210,211,212,213,214,215,
216,217,218,219,220,221,222,223,224,225,226,227,228,229,230,231,
123, 65, 66, 67, 68, 69, 70, 71, 72, 73,232,233,234,235,236,237,
125, 74, 75, 76, 77, 78, 79, 80, 81, 82,238,239,240,241,242,243,
92,159, 83, 84, 85, 86, 87, 88, 89, 90,244,245,246,247,248,249,
48, 49, 50, 51, 52, 53, 54, 55, 56, 57,250,251,252,253,254,255
};
char ASCIItoEBCDIC(const unsigned char c)
{
return a2e[c];
}
char EBCDICtoASCII(const unsigned char c)
{
return e2a[c];
}
在示例文本
char sample[6] = "hello";的情况下，h如何准确地从ascii转换为ebcdic，反之亦然？编辑：我真的不需要转换字符串。我只想知道这些表是如何构造的。
最佳答案
我只想知道这些表是如何构造的。
ASCII中的'0'的代码值为48。
EBCDIC中的'0'的代码值为240。
因此，我们需要将48映射为240并将240映射为48的表。
以ASCII代码值为48转换'0'。a2e[48]返回240，即字符'0'的EBCDIC代码。
static unsigned char a2e[256] = {
...
...
...
240,241,242,243,244,245,246,247,248,249,122, 94, 76,126,110,111,
...
现在使用240，字符
'0'的EBCDIC代码。 e2a[240]，它返回48，即字符'0'的ASCII码。static unsigned char e2a[256] = {
...
13 more rows
...
48, 49, 50, 51, 52, 53, 54, 55, 56, 57,250,251,252,253,254,255
};
对所有其他常见字符执行此操作。将映射定义为能够进行其余操作。回忆ASCII仅定义128个字符，而EBCDIC定义256个字符。
杂记
EBCDIC布局与某些punch cards有某种关系。
在两个字符集中，字符
0，1，... 9是顺序的，这是用C编码的要求。在这两组中，大写字母和小写字母相差1位，因此可以编写以下代码（使用C的
tolower()更好）int from_upper_to_lower(int code) {
return code - 'A' + 'a`;
}
关于c - EBCDIC转换为ASCII的背后原理是什么？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/35491970/