Fix typos in PROGMEM reference page

Author: animeshsrivastava24

Language/Variables/Utilities/PROGMEM.adoc

@@ -21,7 +21,7 @@ Store data in flash (program) memory instead of SRAM. There's a description of t
 
 The `PROGMEM` keyword is a variable modifier, it should be used only with the datatypes defined in pgmspace.h. It tells the compiler "put this information into flash memory", instead of into SRAM, where it would normally go.
 
-PROGMEM is part of the link:http://www.nongnu.org/avr-libc/user-manual/group\__avr__pgmspace.html[pgmspace.h] library. It is included automatically in modern versions of the IDE, however if you are using an IDE version below 1.0 (2011), you'll first need to include the library at the top your sketch, like this:
+PROGMEM is part of the link:http://www.nongnu.org/avr-libc/user-manual/group\__avr__pgmspace.html[pgmspace.h] library. It is included automatically in modern versions of the IDE. However, if you are using an IDE version below 1.0 (2011), you'll first need to include the library at the top your sketch, like this:
 
 `#include <avr/pgmspace.h>`
 While `PROGMEM` could be used on a single variable, it is really only worth the fuss if you have a larger block of data that needs to be stored, which is usually easiest in an array, (or another C++ data structure beyond our present discussion).
@@ -34,7 +34,7 @@ Using `PROGMEM` is also a two-step procedure. After getting the data into Flash
 === Syntax
 `const dataType variableName[] PROGMEM = {data0, data1, data3...};`
 
-Note that because PROGMEM is a variable modifier, there is no hard and fast rule about where it should go, so the Arduino compiler accepts all of the definitions below, which are also synonymous. However experiments have indicated that, in various versions of Arduino (having to do with GCC version), PROGMEM may work in one location and not in another. The "string table" example below has been tested to work with Arduino 13. Earlier versions of the IDE may work better if PROGMEM is included after the variable name.
+Note that because PROGMEM is a variable modifier, there is no hard and fast rule about where it should go, so the Arduino compiler accepts all of the definitions below, which are also synonymous. However, experiments have indicated that, in various versions of Arduino (having to do with GCC version), PROGMEM may work in one location and not in another. The "string table" example below has been tested to work with Arduino 13. Earlier versions of the IDE may work better if PROGMEM is included after the variable name.
 
 `const dataType variableName[] PROGMEM = {};  // use this form` +
 `const PROGMEM dataType variableName[] = {};  // or this one` +
@@ -118,7 +118,7 @@ These tend to be large structures so putting them into program memory is often d
   Setting up a table (array) of strings in program memory is slightly complicated, but
   here is a good template to follow.
 
-  Setting up the strings is a two-step process. First define the strings.
+  Setting up the strings is a two-step process. First, define the strings.
 */
 
 #include <avr/pgmspace.h>