while 1 and fget1 loop.

fide = fopen('data.13o')
head_lines = 0
while 1  
   head_lines = head_lines+1
   line = fgetl(fide)
   answer = findstr(line,'END OF HEADER')
   if ~isempty(answer), break;  end
end

% the header of the data.13o file is;

    OBSERVATION DATA    M                                    RINEX VERSION / TYPE
  LEICA GEO OFFICE 5.0                    10-5-13 10:45       PGM / RUN BY / DATE
                                                              OBSERVER / AGENCY
  O2930689                                                    MARKER NAME
  O2930689                                                    MARKER NUMBER
  P8UO0W21QTC         -Unknown-           -Unknown-           REC # / TYPE / VERS
  -Unknown-           TPSGR3          NONE                    ANT # / TYPE
    4303634.7047  2746069.9471  3812585.4149                  APPROX POSITION XYZ
          1.3289        0.0000        0.0000                  ANTENNA: DELTA H/E/N
  L1PhaOff:   0.2338  L2PhaOff:   0.2252                      COMMENT
       1     1                                                WAVELENGTH FACT L1/2
       7    C1    P1    L1    D1    P2    L2    D2            # / TYPES OF OBSERV
    2013     4    13     4    56   30.000000                  TIME OF FIRST OBS
    2013     4    13     7    59    0.000000                  TIME OF LAST OBS
      16                                                      LEAP SECONDS
      27                                                      # OF SATELLITES
                                                               END OF HEADER

%this loop works what it supposed to be but I couldn't understand how "while 1" works for this loop and what's the difference between "while 1" and while for the loop.

Answer 1

[Guillaume]

while 1 is the same as while true. It means loop forever. The only way to stop the loop is to use a break statement, which is what you're doing with the

 if ~isempty(answer), break; end

Another way to write the loop would have been:

answer = '~'; %anything not empty so the loop starts
while ~isempty(answer)
    head_lines = head_lines+1
    line = fgetl(fide)
    answer = findstr(line,'END OF HEADER')
end

[sanjeet singh]

while 1 and while 2 showing the same result

[Guillaume]

@sanjeet singh

Clearly, you haven't understand what while constant do. There are only two possibilities:

while 0 which is equivalent to while false. The while loop will never execute and,

while any_number_not_0, which is equivalent to while true, the loop will execute forever unless stop with a break. while 1, while 2, while pi, while inf, while 5e10 are all the same.

[Ozan Akyildiz]

@Guillame, I think stating that 0 resolves to false and any other number (or char) will resolve to true is enough. No need to berate.

Answer 2

[d bhaskar]

a=1;

while 1

a=a+1;

if(a>100) break

end

end