c64.h: add c64_basic_run() and c64_basic_load() helper functions

systems/c64.h

@@ -421,8 +421,12 @@ bool c64_is_tape_motor_on(c64_t* sys);
 uint32_t c64_save_snapshot(c64_t* sys, c64_t* dst);
 // load a snapshot, returns false if snapshot versions don't match
 bool c64_load_snapshot(c64_t* sys, uint32_t version, c64_t* src);
-// perform a SYS xxxx BASIC call
-void c64_syscall(c64_t* sys, uint16_t addr);
+// perform a RUN BASIC call
+void c64_basic_run(c64_t* sys);
+// perform a LOAD BASIC call
+void c64_basic_load(c64_t* sys);
+// perform a SYS xxxx BASIC call via the BASIC input buffer
+void c64_basic_syscall(c64_t* sys, uint16_t addr);
 // returns the SYS call return address (can be used to set a breakpoint)
 uint16_t c64_syscall_return_addr(void);
 
@@ -1167,7 +1171,32 @@ bool c64_load_snapshot(c64_t* sys, uint32_t version, c64_t* src) {
     return true;
 }
 
-void c64_syscall(c64_t* sys, uint16_t addr) {
+void c64_basic_run(c64_t* sys) {
+    CHIPS_ASSERT(sys);
+    // write RUN into the keyboard buffer
+    uint16_t keybuf = 0x277;
+    mem_wr(&sys->mem_cpu, keybuf++, 'R');
+    mem_wr(&sys->mem_cpu, keybuf++, 'U');
+    mem_wr(&sys->mem_cpu, keybuf++, 'N');
+    mem_wr(&sys->mem_cpu, keybuf++, 0x0D);
+    // write number of characters, this kicks off evaluation
+    mem_wr(&sys->mem_cpu, 0xC6, 4);
+}
+
+void c64_basic_load(c64_t* sys) {
+    CHIPS_ASSERT(sys);
+    // write LOAD
+    uint16_t keybuf = 0x277;
+    mem_wr(&sys->mem_cpu, keybuf++, 'L');
+    mem_wr(&sys->mem_cpu, keybuf++, 'O');
+    mem_wr(&sys->mem_cpu, keybuf++, 'A');
+    mem_wr(&sys->mem_cpu, keybuf++, 'D');
+    mem_wr(&sys->mem_cpu, keybuf++, 0x0D);
+    // write number of characters, this kicks off evaluation
+    mem_wr(&sys->mem_cpu, 0xC6, 5);
+}
+
+void c64_basic_syscall(c64_t* sys, uint16_t addr) {
     CHIPS_ASSERT(sys);
     // write SYS xxxx[Return] into the keyboard buffer (up to 10 chars)
     uint16_t keybuf = 0x277;