Added documentation to console.c

.gitignore

@@ -13,6 +13,8 @@ compile_commands.json
 .vscode/
 .idea/
 *~
+.pyc
+*.pyc
 
 # QEMU / debug
 *.log

kernel/arch/x86_64/console.c

@@ -13,8 +13,13 @@
 static uint8_t cursor_row;
 static uint8_t cursor_col;
 
+/* Text buffer: one 16-bit cell per character, low byte is the ASCII code,
+ * high byte is the color attribute. `volatile` so the compiler keeps every
+ * store in order: this is memory-mapped I/O, and dropped or reordered
+ * writes would corrupt the screen. */
 static volatile uint16_t *const vga = (uint16_t *)VGA_ADDR;
 
+/* Move every line one row up and blank the last line */
 static void scroll(void)
 {
     for (uint8_t row = 1; row < VGA_HEIGHT; row++) {
@@ -47,10 +52,12 @@ void console_putchar(char c)
             (uint16_t)((COLOR_DEFAULT << 8) | c);
         cursor_col++;
         if (cursor_col >= VGA_WIDTH) {
+            /* Past the right edge: wrap to the next line. */
             cursor_col = 0;
             cursor_row++;
         }
     }
+    /* Past the bottom line: scroll and stay on the last line. */
     if (cursor_row >= VGA_HEIGHT) {
         scroll();
         cursor_row = VGA_HEIGHT - 1;
@@ -70,6 +77,7 @@ void console_puthex64(uint64_t value)
     static const char digits[] = "0123456789ABCDEF";
 
     console_puts("0x");
+    /* Print 16 nibbles, most significant first (shifts 60, 56, …, 0). */
     for (int shift = 60; shift >= 0; shift -= 4) {
         console_putchar(digits[(value >> shift) & 0xFU]);
     }