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Perry Kivolowitz 2023-01-13 08:18:09 -06:00
parent ad1ee3599c
commit 3337e122cc
3 changed files with 62 additions and 19 deletions
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28
.vscode/settings.json vendored
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@ -33,19 +33,21 @@
"MD024":false "MD024":false
}, },
"cSpell.ignoreWords": [ "cSpell.ignoreWords": [
"Rypo", "Athanasios",
"dless", "Pavlidis",
"dmore", "Rypo",
"foov", "dless",
"ndless", "dmore",
"ndmore", "foov",
"onditionally", "ndless",
"onsole", "ndmore",
"rotypo", "onditionally",
"rwtypo", "onsole",
"slen", "rotypo",
"ssize" "rwtypo",
], "slen",
"ssize"
],
"files.associations": { "files.associations": {
"ostream": "cpp" "ostream": "cpp"
} }

28
section_3/endian/README.md
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@ -156,8 +156,25 @@ on a little endian machine, it is the first byte in the long in memory.
## Output on a big endian machine ## Output on a big endian machine
We tried and tried but could not get anyone to run this code on a We tried and tried to find a kind soul to run the above program on a
big-endian machine. big-endian machine. Redditor Athanasios Pavlidis ran a C version of the
code on both an Amiga A4000/MC68040 and an Amiga A3000/MC68030. The
results were:
```text
Endianness of this computer:
i16: 0123
i32: 01234567
i64: 89abcdef01234567
```
Notice the values for `i16` and `i32` match the right hand column above.
The value for `i64` is borked in that we specified it in the C code as a
`long`. We then tried specifying the `long` as a `long long`. Apparently
there is little support for 64 bit numbers on this ancient but
venerable architecture.
Athanasios Pavlidis has our appreciation and thanks.
## Can't the ARM swing both ways? ## Can't the ARM swing both ways?
@ -169,7 +186,8 @@ install the big-endian version of the toolchain.
Here is a quote from Wikipedia: Here is a quote from Wikipedia:
```text ```text
ARM, C-Sky, and RISC-V have no relevant big-endian deployments, and can be considered little-endian in practice. ARM, C-Sky, and RISC-V have no relevant big-endian deployments, and can
be considered little-endian in practice.
``` ```
## What is Intel? ## What is Intel?
@ -178,6 +196,4 @@ The common Intel processors are also little-endian.
## So what's big-endian? ## So what's big-endian?
The Motorola 68K family - we reached out to the Amiga user community in IBM mainframes and the Motorola 68K family come to mind. See above.
the hopes that someone would run the code, but no one has and this makes
us sad. :(

25
section_3/endian/main.c Normal file
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@ -0,0 +1,25 @@
#include <stdio.h>
void Dump(void * i, int length) {
unsigned char * ptr = (unsigned char *) i;
for (int counter = 0; counter < length; counter++) {
printf("%02x", *(ptr++));
}
printf("\n");
}
int main() {
unsigned short i16 = 0x0123;
unsigned int i32 = 0x01234567;
unsigned long i64 = 0x0123456789ABCDEF;
printf("Endianness of this computer:\n");
printf("i16: ");
Dump((void *) &i16, 2);
printf("i32: ");
Dump((void *)&i32, 4);
printf("i64: ");
Dump((void *)&i64, 8);
return 0;
}