Solutions

1.	$ grep ZZZ memo
	$ echo $?
	1
	$ grep and memo
	$ echo $?
	0

2.	#!/bin/bash
	# File: president1	
	for pres in Washington Jefferson Lincoln Kennedy Clinton
	do
	   echo $pres
	done

3.	#!/bin/bash
	# File: president2	
	for pres in Washington Jefferson Lincoln Kennedy Clinton
	do
   	   echo $pres
   	   if [ $pres = Lincoln ] ; then
      	      echo "Call me Abe"
   	   fi
	done

4.	#!/bin/bash
	# File: president3	
	for pres in Washington Jefferson Lincoln Kennedy Clinton
	do
   	   echo $pres
   	   if [ $pres = Washington ] ; then
      	      echo "Call me George"
   	   elif [ $pres = Jefferson ] ; then
      	      echo "Call me Tom"
   	   elif [ $pres = Lincoln ] ; then
      	      echo "Call me Abe"
   	   elif [ $pres = Kennedy ] ; then
      	      echo "Call me Jack (if you are my friend)"
   	   elif [ $pres = Clinton ] ; then
      	      echo "Call me Wild William"
   	   fi
	done
