Add readkey for C64 & ZXS. Fix putchar('{q}') on C64.

docs/stdlib/frequent.md

@@ -8,16 +8,34 @@ However, as they are not the part of the standard library, they might not be ava
 
 Prints a single character.
 
-Available for: all computer targets.
+Available for: all computer targets.  
+Uses ROM routines, so requires the appropriate ROM to be enabled if applicable.
 
-Note that this function obeys typical platform idiosyncrasies,
+Note that this function may obey typical platform idiosyncrasies, for example:
-for example on CBM targets the quote character will toggle the quotation mode.
+
+* on CBM targets other than C64 the quote character toggles the quotation mode
+
+* printing past the end of line might insert a blank line below the current one
+
+* printing past the end of the screen might ask the user to confirm scrolling
+
+The exact behaviour is platform-dependent.
+Future library versions will strive to eliminate those issues.
 
 #### `void new_line()`
 
 Moves the cursor to the next line.
 
-Available for: all computer targets.
+Available for: all computer targets.  
+Uses ROM routines, so requires the appropriate ROM to be enabled if applicable.
+
+#### `byte readkey()`
+
+Waits for and reads a single keypress.
+
+Available for:
+Commodore 64 (requires KERNAL),
+ZX Spectrum.
 
 #### `pointer readline()`
 
@@ -28,8 +46,8 @@ Available for:
 ZX Spectrum,
 NEC PC-88,
 MSX,
-Commodore 64 with `c64_basic` module,
+Commodore 64 with `c64_basic` module (requires KERNAL and BASIC),
-Commodore 16 or Plus/4 with `c264_basic` module.
+Commodore 16 or Plus/4 with `c264_basic` module (requires KERNAL and BASIC).
 
 #### `word readword()`
 
@@ -39,14 +57,15 @@ Available for:
 ZX Spectrum,
 NEC PC-88,
 MSX,
-Commodore 64 with `c64_basic` module,
+Commodore 64 with `c64_basic` module (requires KERNAL and BASIC),
-Commodore 16 or Plus/4 with `c264_basic` module.
+Commodore 16 or Plus/4 with `c264_basic` module (requires KERNAL and BASIC).
 
 #### `void bell()`
 
 Beeps.
 
 Available for: Apple 2, ZX Spectrum.
+Uses ROM routines, so requires the appropriate ROM to be enabled if applicable.
 
 #### `void set_bg_color(byte color)`
 

docs/stdlib/stdio.md

@@ -4,14 +4,12 @@
 
 The `stdio` module automatically imports the `string` and `err` modules.  
 It requires an implementation of `void putchar(byte a)` and therefore works only on targets with console output.
+On targets with idiosyncratic behaviour of `putchar`, functions in this module inherit that behaviour.
 
 #### `void putstr(pointer str, byte len)`
 
 Prints a string of length `len` located at address `str`.  
 
-Note that both this function and `putstrz` obey typical platform idiosyncrasies,
-for example on CBM targets the quote character will toggle the quotation mode. This may be subject to change.
-
 #### `void putstrz(pointer str)`
 
 Prints a null-terminated string located at address `str`.  

include/c64_kernal.mfk

@@ -2,11 +2,12 @@
 
 // CHROUT. Write byte to default output. (If not screen, must call OPEN and CHKOUT beforehands.)
 // Input: A = Byte to write.
-asm void putchar(byte a) @$FFD2 extern
+asm void chrout(byte a) @$FFD2 extern
 
 // CHRIN. Read byte from default input (for keyboard, read a line from the screen). (If not keyboard, must call OPEN and CHKIN beforehands.)
 // Output: A = Byte read.
-asm byte getchar() @$FFCF extern
+asm byte chrin() @$FFCF extern
+alias getchar = chrin
 
 // CHKIN. Define file as default input. (Must call OPEN beforehands.)
 // Input: X = Logical number.
@@ -23,8 +24,22 @@ asm void clrchn() @$FFCC extern
 // Output: A = Device status.
 asm byte readst() @$FFB7 extern
 
+inline asm void putchar(byte a) {
+    JSR chrout
+    LDA #0
+    STA $D4
+    ? RTS
+}
+
+noinline asm byte readkey() {
+__read_key__start
+    LDA $C6
+    BEQ __read_key__start
+    JMP $E5B4
+}
+
 inline void new_line() {
-    putchar(13)
+    chrout(13)
 }
 
 // OPEN. Open file. (Must call SETLFS and SETNAM beforehands.)

include/zxspectrum.mfk

@@ -14,6 +14,16 @@ inline void new_line() {
     putchar(13)
 }
 
+asm byte readkey() {
+    ld hl,23560
+    ld (hl),0
+__readkey__start:
+    ld a,(hl)
+    or a
+    jr z,__readkey__start
+    ? ret
+}
+
 inline asm void set_border(byte a) {
     out (254),a
     ? ret