mention the `disassemble` GDB command

doc/Quickstart.md

@@ -88,7 +88,7 @@ commands check out the [troubleshooting guide][troubleshoot].
 $ # fetch the Cargo project template
 $ cargo clone cortex-m-quickstart
 
-$ # rename it as you wish
+$ # rename it as you wish (remember this name! you'll use it later)
 $ mv cortex-m-quickstart app
 
 $ cd app
@@ -414,6 +414,21 @@ about to execute using the `list` command:
 340             #[cfg(not(has_fpu))]
 ```
 
+And you can print the machine code that the processor is about to execute using the `disassemble`
+command.
+
+``` console
+(gdb) disassemble
+Dump of assembler code for function cortex_m_rt::reset_handler:
+   0x08000130 <+0>:     push    {r7, lr}
+   0x08000132 <+2>:     mov     r7, sp
+   0x08000134 <+4>:     sub     sp, #32
+=> 0x08000136 <+6>:     movw    r0, #0
+   0x0800013a <+10>:    movw    r1, #0
+   0x0800013e <+14>:    movt    r0, #8192       ; 0x2000
+   0x08000142 <+18>:    movt    r1, #8192       ; 0x2000
+```
+
 We can skip to our program `main` by creating a breakpoint and then calling `continue`.
 
 ``` console
@@ -461,7 +476,7 @@ xPSR: 0x01000000 pc: 0x08000400 msp: 0x20005000, semihosting
 
 This is the same command we ran before from the `telnet` prompt.
 
-You can find the list of all the GDB commands [here][gdb-commands].
+Tip: You can get  list of all the GDB commands by entering `help all` in the GDB prompt.
 
 Note that semihosting is *very slow*. Each write operation takes *hundreds* of milliseconds; the
 processor will be in a halted state for the duration of the write operation. Semihosting is nice