在網路上看到了一些關於 ctype.h 一些 macro，這裡做些摘錄
#define is_digit(c) ((c)>='0' && (c)<='9')
#define is_digit(c) ((unsigned)(c) - '0' <= 9)
#define is_alpha(c) (((c) < CTLESC || (c) > CTLENDARI) && isalpha((unsigned char) (c)))
#define is_name(c) (((c) < CTLESC || (c) > CTLENDARI) && ((c) == '_' || isalpha((unsigned char) (c))))
#define is_in_name(c) (((c) < CTLESC || (c) > CTLENDARI) && ((c) == '_' || isalnum((unsigned char) (c))))
#define is_special(c) ((is_type+SYNBASE)[c] & (ISSPECL|ISDIGIT))
#define is_special(c) (is_digit(c)||c=='!'||c=='#'||c=='$'||c=='*'||c=='-')
#define digit_val(c) ((c) - '0')
關於一些 NULL, BEL 之輸入，可在這個網站找到相關說明，截錄如下
| Char | Oct | Dec | Hex | Control-Key | Control Action |
|---|---|---|---|---|---|
| NUL | 0 | 0 | 0 | ^@ | NULl character |
| SOH | 1 | 1 | 1 | ^A | Start Of Heading |
| STX | 2 | 2 | 2 | ^B | Start of TeXt |
| ETX | 3 | 3 | 3 | ^C | End of TeXt |
| EOT | 4 | 4 | 4 | ^D | End Of Transmission |
| ENQ | 5 | 5 | 5 | ^E | ENQuiry |
| ACK | 6 | 6 | 6 | ^F | ACKnowledge |
| BEL | 7 | 7 | 7 | ^G | BELl, rings terminal bell |
| BS | 10 | 8 | 8 | ^H | BackSpace (non-destructive) |
| HT | 11 | 9 | 9 | ^I | Horizontal Tab (move to next tab position) |
| LF | 12 | 10 | a | ^J | Line Feed |
| VT | 13 | 11 | b | ^K | Vertical Tab |
| FF | 14 | 12 | c | ^L | Form Feed |
| CR | 15 | 13 | d | ^M | Carriage Return |
| SO | 16 | 14 | e | ^N | Shift Out |
| SI | 17 | 15 | f | ^O | Shift In |
| DLE | 20 | 16 | 10 | ^P | Data Link Escape |
| DC1 | 21 | 17 | 11 | ^Q | Device Control 1, normally XON |
| DC2 | 22 | 18 | 12 | ^R | Device Control 2 |
| DC3 | 23 | 19 | 13 | ^S | Device Control 3, normally XOFF |
| DC4 | 24 | 20 | 14 | ^T | Device Control 4 |
| NAK | 25 | 21 | 15 | ^U | Negative AcKnowledge |
| SYN | 26 | 22 | 16 | ^V | SYNchronous idle |
| ETB | 27 | 23 | 17 | ^W | End Transmission Block |
| CAN | 30 | 24 | 18 | ^X | CANcel line |
| EM | 31 | 25 | 19 | ^Y | End of Medium |
| SUB | 32 | 26 | 1a | ^Z | SUBstitute |
| ESC | 33 | 27 | 1b | ^[ | ESCape |
| FS | 34 | 28 | 1c | ^\ | File Separator |
| GS | 35 | 29 | 1d | ^] | Group Separator |
| RS | 36 | 30 | 1e | ^^ | Record Separator |
| US | 37 | 31 | 1f | ^_ | Unit Separator |
另外有些心得也放上來
0. 範圍
A~Z: 41H~5AH (0100 0001~0101 1010)
a~z: 61H~7AH (0110 0001~0111 1010)
0~9: 30H~39H (0011 0000~0011 1001)
1. 大寫轉小寫
#define BITMASK 0x20 char ch = 'A'; ch |= BITMASK
2. 小寫轉大寫
#define BITMASK (~(0x20)) char ch = 'a'; ch &= BITMASK
3. 字元'0'~'9' 轉整數
int x; char ch; x=ch & 0x0F;
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