Uppercase A
- Input
- A
- Expected output
- DEC 65 · HEX 41 · BIN 01000001
This is the code the table uses as a reference point: a two-digit hexadecimal and an eight-digit binary, the fixed width of one full byte.
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ascii decimal hexadecimal binary
Every ASCII character is, underneath, a number from 0 to 127, and this page shows that same number in three bases side by side: decimal, hexadecimal and binary. It is the exact conversion that comes up constantly in text debugging, byte tables and code that tests a specific bit inside a character.
This is the code the table uses as a reference point: a two-digit hexadecimal and an eight-digit binary, the fixed width of one full byte.
Compare it against the previous example: only the fifth bit changes, and the decimal gap between the two is always 32 for any matching letter pair.
0x30 is the classic offset used to read a text digit as a number, a technique still common in hand-written parsers.
No. ASCII covers only 128 codes. Unicode covers nearly all modern writing systems. The first 128 Unicode code points preserve ASCII compatibility, which makes every ASCII text a valid UTF-8 text as well.
Because one byte covers values from 0 to 255, and the largest of those in hexadecimal is FF, two digits; padding with a leading zero (0x07 instead of 0x7) keeps every code the same width, which makes a sequence of bytes much easier to read in a column.
Because the original ASCII standard reserved the fifth bit, counted from the left, exactly for that distinction: with that bit at 0 the letter is uppercase, with it at 1 the letter is lowercase, and the numeric difference of a single bit in that position is always 32.
Because each hexadecimal digit stands for exactly 4 bits, so two digits cover a full byte without losing any information; the eight binary digits of 01000001 collapse into just two characters, 41, which are far easier to type and compare at a glance.
By the prefix or the digit range: hexadecimal usually carries a 0x prefix and uses digits 0 through 9 plus letters A through F, binary only ever uses 0 and 1, and plain decimal with no prefix is this table default reading.
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