Greg Hewgill
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How did old MS-DOS games utilize various graphic cards?
Accepted answer
70 votes

Did every programmer of every game implemented all possible various API's that old graphic cards supported? Yes - but it went even deeper than that. Early graphics cards had virtually no callable ...

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Why is the Intel 8086 CPU called a 16-bit CPU?
65 votes

Generally, the "bitness" of a CPU is determined by the usual or common size of its data registers (or, the width of its data bus), rather than the width of the address bus. There are exceptions, for ...

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Why wasn't ASCII designed with a contiguous alphanumeric character order?
61 votes

According to ASA X3.4-1963 Appendix A, one of the design considerations was: (7) Ease in the identification of classes of characters Furthermore: A4.4 The character set was structured to enable ...

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Strange math syntax in old basic listing
Accepted answer
60 votes

Your mention of TRS-80 provides a clue. In the TRS-80 character set, the space normally occupied by the ASCII [ character is instead a ↑ (up arrow) character. Old versions of BASIC (such as this one ...

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Why did the VIC-20 and C64 have only 22 and 40 columns when the earlier PET had 80 column text?
58 votes

One reason was likely that the VIC-20 and C64 did not have their own displays, but were designed to be connected to a television set. The interface between the computer and the television was not ...

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What was the design rationale behind multi-port and multiple connections (and back-connections) designs of the early protocols like NFS or FTP?
54 votes

At least for FTP, the actual file transfer happened over a different connection to support a particular file transfer mode that isn't used much today. Suppose you have three machines, A, B, C, and you ...

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Why (historically) include the number of arguments (argc) as a parameter of main?
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45 votes

K&R first edition (1978) does not mention the NULL terminator in the argv list at all. This was added later, in ANSI C. The relevant paragraph (section 5.11, p. 110) is: In environments that ...

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What is the difference between the "Return" and "Enter" keys in the VT100 terminal?
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31 votes

Under normal circumstances, there is no difference (RETURN and ENTER will send CR or CR LF as configured by the New Line Mode). However, there is a mode called "keypad application mode" ...

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Does the Intel 8085 CPU use real memory addresses?
27 votes

The 8085 is effectively the same as the 8080 microprocessor. The 8080 has a flat 16-bit address space and no segment registers. So yes, the 8085 uses real memory addresses without any translation.

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What was the service offered by US Sprint for long distance data connections in the late 1980's?
Accepted answer
19 votes

It sounds like what you're looking for is Telenet (renamed to "Sprintnet" when Sprint acquired it) or Tymnet. Tymnet did not survive and Sprintnet became part of what we now know as the Internet.

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Why did C have the return type before functions?
14 votes

Typically with questions like this, it's very difficult to determine the exact reason why a past design decision was made. This decision would have been made very early on in the development of C, and ...

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What was the second most common incompatibility in MS-DOS machines?
11 votes

Aspects I recall, perhaps influenced by the area I was working in at the time: Video display (as you mention) Serial ports Timer interrupt I only had to work with "near-compatible" ...

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Turn off Apple IIe sound
Accepted answer
10 votes

In this case, to "toggle" the speaker means to move it from one position to the other. To make a sound, you repeatedly toggle the speaker (by poking that address) at a particular speed to make a sound ...

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How did humans interact with early computers without screens or sensors?
5 votes

There have been many different kinds of I/O devices since the early years: Indicator lights (often coloquially referred to as "blinkenlights") Front panel toggle switches and pushbuttons Punched tape ...

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Why did ISDN terminals tend to advertise the switches they are compatible with vs the standard protocols?
4 votes

From memory (it was a few decades ago...) the ISDN situation in North America was not particularly uniform. Some of the big switch vendors (like AT&T) had flavors of ISDN that were kind of mostly ...

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How do Bulletin Board Systems work?
4 votes

Back before the Internet, BBS systems were accessed by dialup modem connections. The caller would dial the phone number of the BBS, where it would connect to a modem (and then to the computer through ...

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Why VGA framebuffer was limited to 64kB window?
3 votes

In the 16-bit 8086, addressing of the memory space was done with a two-register pair Segment:Offset. The Segment register (there were four of them) addressed the high 16 bits of the 20-bit addressable ...

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Why does the Commodore 64 leave these pointers in Zeropage?
3 votes

These function pointers are in zero page RAM because that leaves the manufacturer the ability to change the ROM without affecting software that already uses those functions through the zero page ...

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Resource for 6502 assembly directives?
3 votes

What you're calling "directives" are not related to the actual CPU instructions. That is, they are not "6502 directives". Instead, each specific assembler had different ways of specifying things like ...

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How do I round up on a TI-84+
1 votes

Add one and then round down. But make sure the number is not already an integer, because adding 1 and then rounding down would end up adding 1.

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