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In some printers, the high bit was used to enable Italics printing.
The standards committee decided against shifting, and so ASCII required at least a seven-bit code.
Lowercase letters were therefore not interleaved with uppercase.
To keep options available for lowercase letters and other graphics, the special and numeric codes were arranged before the letters, and the letter A was placed in position 41 The digits 0–9 are prefixed with 011, but the remaining 4 bits correspond to their respective values in binary, making conversion with binary-coded decimal straightforward.
The The control codes felt essential for data transmission were the start of message (SOM), end of address (EOA), end of message (EOM), end of transmission (EOT), "who are you? " (RU), a reserved device control (DC0), synchronous idle (SYNC), and acknowledge (ACK).
These were positioned to maximize the Hamming distance between their bit patterns.