I used this code to read txt file I want to use It to make volcano graph

genelist<-read.table("fexam1.txt", header=TRUE)

but it gives me error like

Error in scan(file = file, what = what, sep = sep, quote = quote, dec = dec,  : 
  line 69 did not have 3 elements

for almost every file

can you tell me whats wrong

The error message gives you a pretty good hint here - line 69 of your file does not contain 3 elements.  It has determined that there should be 3 columns of data from the first line in the file, since you specified header = TRUE

I would suggest looking at that line to understand why this is happening.  By default read.table() defines a new column every time it encounters white space.  Perhaps you have a space in that line that isn't present on the other lines?  You can use the argument sep to break on other characters.  This example would split data when it finds a tab.

genelist <- read.table("fexam1.txt", header = TRUE, sep = "\t")

For more details you can read the help file for the function with 

?read.table