Notes on endianness.

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notes/_journal/2024-02-11.md

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 title: "2024-02-11"
 ---
 
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+- [x] Anki Flashcards
+- [x] KoL
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 - [ ] OGS (1 Life & Death Problem)
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+
+* Notes on endianness.

notes/binary/endianness.md

@@ -0,0 +1,119 @@
+---
+title: Endianness
+TARGET DECK: Obsidian::STEM
+FILE TAGS: binary::endian
+tags:
+  - binary
+  - endian
+---
+
+## Overview
+
+Platforms with multi-byte objects must establish the object's address and byte ordering. Objects are typically addressed by the smallest address of the bytes used. Bytes are ordered either in **big-endian** or **little-endian**. In big-endian, the most significant byte is listed first. In little-endian, the least significant byte is ordered first.
+
+%%ANKI
+Basic
+Platforms with multi-byte objects must establish what two conventions?
+Back: The object's address and byte ordering.
+Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
+<!--ID: 1707661283766-->
+END%%
+
+%%ANKI
+Basic
+How are multi-byte objects typically addressed?
+Back: By the smallest address of the bytes used.
+Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
+<!--ID: 1707661283768-->
+END%%
+
+%%ANKI
+Basic
+How are bytes of multi-byte objects typically ordered?
+Back: As big-endian or little-endian.
+Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
+<!--ID: 1707661283770-->
+END%%
+
+%%ANKI
+Basic
+What is endianness?
+Back: The ordering of bytes of a multibyte object.
+Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
+<!--ID: 1707661283771-->
+END%%
+
+%%ANKI
+Basic
+What does it mean for a byte to be "most significant"?
+Back: It contribute most to the byte's (decimal) value.
+Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
+<!--ID: 1707661283773-->
+END%%
+
+%%ANKI
+Basic
+What does it mean for a byte to be "least significant"?
+Back: It contribute least to the byte's (decimal) value.
+Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
+<!--ID: 1707661283774-->
+END%%
+
+%%ANKI
+Basic
+What does it mean to be big-endian?
+Back: The most significant byte is ordered first.
+Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
+<!--ID: 1707661283776-->
+END%%
+
+%%ANKI
+Basic
+What does it mean to be little-endian?
+Back: The least significant byte is ordered first.
+Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
+<!--ID: 1707661283777-->
+END%%
+
+%%ANKI
+Basic
+How are bytes of `int32_t x = 0x01234567` written in big-endian?
+Back: `0x01 0x23 0x45 0x67`
+Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
+Tags: c
+<!--ID: 1707661283779-->
+END%%
+
+%%ANKI
+Basic
+How are bytes of `int32_t x = 0x01234567` written in little-endian?
+Back: `0x67 0x45 0x23 0x01`
+Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
+Tags: c
+<!--ID: 1707661283780-->
+END%%
+
+%%ANKI
+Cloze
+Many microprocessors chips are {bi-endian} meaning they can be {configured as either big- or little-endian}.
+Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
+<!--ID: 1707661283782-->
+END%%
+
+```c
+#include <stdint.h>
+#include <stdio.h>
+
+int main() {
+  int32_t x = 0x01234567;
+  for (int i = 0; i < 4; ++i) {
+    printf("%.2x ", ((unsigned char *)(&x))[i]);
+  }
+}
+```
+
+The above snippet can be used to check endianness on the current machine. If big-endian, the output should be `01 23 45 67`. If little-endian, `67 45 23 01`.
+
+## Reference
+
+* Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.

notes/binary/hexadecimal.md

@@ -224,4 +224,4 @@ END%%
 
 ## Reference
 
-* Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
+* Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.

notes/c/declarations.md

@@ -36,6 +36,22 @@ Back: It can only represent nonnegative values.
 Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
 END%%
 
+%%ANKI
+Basic
+How large is a word?
+Back: This is a machine-dependent value.
+Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
+<!--ID: 1707657889227-->
+END%%
+
+%%ANKI
+Basic
+What word sizes are typically nowadays?
+Back: 32- and 64-bit word sizes.
+Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
+<!--ID: 1707657889230-->
+END%%
+
 %%ANKI
 Cloze
 `char` *typically* represents {1} byte(s) on a 64-bit platform.