This is TeX, WAITS Version 2.0 (preloaded format=plain 86.1.22)  27 JAN 1986 16:36
**\tracingall

*{\font\a=cmr5 \global\a}\showthe\font
{begin-group character {}
{\font}
{\global}
{end-group character }}
{restoring \a=undefined}
{\showthe}
> \a .
<recently read> \font 
                      
<*> {\font\a=cmr5 \global\a}\showthe\font
                                         
? 

*\show\a
{\show}
> \a=undefined.
<*> \show\a
           
? 

*\the\font
{\the}
{select font cmr5}

*b\showlists
{the letter b}
{horizontal mode: the letter b}
{\showlists}

### horizontal mode entered at line 0
\hbox(0.0+0.0)x20.0
\a b
spacefactor 1000
### vertical mode entered at line 0
prevdepth ignored

! OK.
<*> b\showlists
               
? 

*\font\A=cmr6 \font\B=cmr6 \let\B=\undefined \showthe\A \the\A
{\font}
{\font}
{\let}
{\showthe}
> \B .
<recently read> \A 
                   
<*> ...6 \font\B=cmr6 \let\B=\undefined \showthe\A
                                                   \the\A
? 
{\the}
{select font cmr6}

*c\showlists
{the letter c}
{\showlists}

### horizontal mode entered at line 0
\hbox(0.0+0.0)x20.0
\a b
\B c
spacefactor 1000
### vertical mode entered at line 0
prevdepth ignored

! OK.
<*> c\showlists
               
? x
 
Here is how much of TeX's memory you used:
 4 strings out of 1574
 31 string characters out of 12510
 22816 words of memory out of 48028
 998 multiletter control sequences out of 2500
 20136 words of font info for 68 fonts, out of 25000 for 100
 14 hyphenation exceptions out of 307
 1i,0n,0p,64b,7s stack positions out of 200i,40n,60p,500b,600s
No pages of output.